How can we view the statement that “life must be understood backwards but must be lived forwards" from a Buddhist perspective?

Obviously, most (learned) wisdom comes from past experience (including meditation experience). However, wisdom also comes from looking forward (such as contemplation of death). Wisdom of past & future crystallize as living in the (passing) 'present'.

There are those who do not realize that one day we all must die. But those who do realize this settle their quarrels.

Dhammapada 6

There is a very important word in Dhamma called “Pratyaveksha”. Sadly I have never come across any explanation of the meaning of this word in english. In Soren Kierkegaard’s saying “life must be understood backwards but must be lived forwards" if you substitute the word “Life” with “our experience of volitional actions”, it gives the closest meaning to the word “Pratyaveksha”. So in re-phrasing Soren Kierkegaard’s saying “our experience of volitional actions must be understood backwards but must be lived forwards”, the saying becomes one of Dhamma. Kierkegaard would quietly bring his readers into a position where the truth of their life was available for their own individual realization, though ultimately it was up to them whether or not to embrace that realization. This is the same in Dhamma. Only the few Dhamma Farers that do “Pratyaveksha” will get to go further in this Noble Eightfold Path in this short lifespan of theirs. In this Dhamma path too we are faced with reflection and action simultaneously.

If one is to reflect on the two qualities “Ehipassiko” and “Opanayiko” of Dhamma, Ehi-passiko means inviting any wise person to come and see. Ehipassiko (Sanskrit: Ehipaśyika "which you can come and see" -- from the phrase ehi, paśya "come, see!"). The Dhamma welcomes all beings to put it to the test by applying it to their own lives and seeing its effects. Then the term “Opanayiko” means each person must practice the teachings and realize their value within one's own experience. Opanayiko (Sanskrit: Avapraṇayika "leading one close to"). The Dhamma is capable of being entered upon and therefore it is worthy to be followed as a part of one's life. So just as Soren Kierkegaard’s saying dhamma confronts each and every individual, independently for him or her self. It's truth is between the individual and his or hers meditative self, and cannot be mediated by thought or society.

Another way to see Soren Kierkegaard’s saying is through Kamma. It is this doctrine of Kamma that can explain the problem of suffering, the mystery of so-called fate or predestination of other religions, and above all the inequality of mankind. As some Westerners prefer to say Kamma is "action-influence." We reap what we have sown. What we sow we reap somewhere or some when. In one sense we are the result of what we were; we will be the result of what we are. In another sense, we are not totally the result of what we were and we will not absolutely be the result of what we are. For instance, a criminal today may be a saint tomorrow. So even if we live forwards righteously and with purpose and dedication, the results that we reap may not be in keeping with our expected results. Only the ones who believe in Kamma will see another side to this saying. Even in life they will have a different perspective to life. They will sympathise with each other and see that all human beings are of equal value, they find it easy to be forgiving and to live with one another in peace. They don’t despise one another for belonging to this or that class or for having only this or that much wealth – all of which are simply a matter of each person’s kamma. After all, no one wants to be poor or stupid. Everyone wants to be intelligent, wealthy, and highly respected. But when it isn’t possible, we have to leave it to the truth that living beings differ in their kamma. Whatever past kamma you have, you experience it and make use of it in line with what you’ve got. If we can forgive each other, with the thought that each living being has his or her own kamma, we can live together in peace. If we believe in the Dhamma, we have to believe in kamma and not in the defilements that make us arrogant and proud.

This saying can also be seen through “Sanskara”. The terms Mental Formation and Volition are used together because each of these terms represents one half of the meaning of sanskara – mental formation represents the half that comes from the past, and volition represents the half that functions here and now.

We live forward

This is equatable to Right Effort because Right Effort is related to exertion to decrease evil and increase good in the here and now ("forward").

but we understand backward.

This is equatable to Right View because one's Right View is greatly enhanced by thinking about one's past karma, chain of causation, and marks of existence.

As with all verbiage, Kierkegaard is 90% right in his statement.

There are things your past that you must take "action" for through hypnotherapy. You have to relive your past and try to find out why this-and-that happened and can unwind that behavior. After you do this you will actually become free of that behavior and can finally get your swag back.

Conversely, there are things in the future that you must understand before you can live it.

I feel that the answer that is most akin to Buddhism comes from the Buddha's instruction to his son to determine what caused the action by reflecting back, and then take responsibility for the action as one moves forward, stated as follows:

The Buddha: How do you construe this, Rahula: What is a mirror for?

Rahula: For reflection, sir.

The Buddha: In the same way, Rahula, bodily acts, verbal acts, and mental acts are to be done with repeated reflection.

Whenever you want to perform a bodily act, you should reflect on it: 'This bodily act I want to perform-would it lead to self-affliction, to the affliction of others, or to both? Is it an unskillful bodily act, with painful consequences, painful results?' If, on reflection, you know that it would lead to self-affliction, to the affliction of others, or to both; it would be an unskillful bodily act with painful consequences, painful results, then any bodily act of that sort is absolutely unfit for you to do. But if on reflection you know that it would not cause affliction...it would be a skillful bodily act with happy consequences, happy results, then any bodily act of that sort is fit for you to do. (Similarly with verbal acts and mental acts.)

While you are performing a bodily act, you should reflect on it: 'This bodily act I am doing-is it leading to self-affliction, to the affliction of others, or to both? Is it an unskillful bodily act, with painful consequences, painful results?' If, on reflection, you know that it is leading to self-affliction, to affliction of others, or both...you should give it up. But if on reflection you know that it is not...you may continue with it. (Similarly with verbal acts and mental acts.)

Having performed a bodily act, you should reflect on it....If, on reflection, you know that it led to self-affliction, to the affliction of others, or to both; it was an unskillful bodily act with painful consequences, painful results, then you should confess it, reveal it, lay it open to the Teacher or to a knowledgeable companion in the holy life. Having confessed it...you should exercise restraint in the future. But if on reflection you know that it did not lead to affliction...it was a skillful bodily act with happy consequences, happy results, then you should stay mentally refreshed and joyful, training day and night in skillful mental qualities. (Similarly with verbal acts.)

Having performed a mental act, you should reflect on it....If, on reflection, you know that it led to self-affliction, to the affliction of others, or to both; it was an unskillful mental act with painful consequences, painful results, then you should feel horrified, humiliated, and disgusted with it. Feeling horrified... you should exercise restraint in the future. But if on reflection you know that it did not lead to affliction...it was a skillful mental act with happy consequences, happy results, then you should stay mentally refreshed and joyful, training day and night in skillful mental qualities.

Rahula, all the priests and contemplatives in the course of the past who purified their bodily acts, verbal acts, and mental acts, did it through repeated reflection on their bodily acts, verbal acts, and mental acts in just this way.

All the priests and contemplatives in the course of the future...All the priests and contemplatives at present who purify their bodily acts, verbal acts, and mental acts, do it through repeated reflection on their bodily acts, verbal acts, and mental acts in just this way.
Therefore, Rahula, you should train yourself: 'I will purify my bodily acts through repeated reflection. I will purify my verbal acts through repeated reflection. I will purify my mental acts through repeated reflection.' Thus you should train yourself. That is what the Blessed One said. Pleased, Ven. Rahula delighted in the Blessed One's words.

M.61