Living worried about the future and reaching mindfulness

The mind's nature is to roll in the future or past. Nothing to get too upset about. What you have to train it is to live in the present moment.

Only way you can overcome this is:

• repeated application
• sustained application

... bringing your mind to the present moment.

When ever your mind wonders away:

• realise that it has wondered away.
• bring it back to the chosen object with no aggregation, disappointment. If any such tension does arises realize it too.

Keep doing it until this becomes second nature and effortless.

Then you will be in the present moment and many of your worries will go away.

Also the concept of impermanence is that the world / universe is in a flux of change. Weather, people, neighborhoods, etc. all keep changing. It is not that the world or universe will come to an abrupt end. Nothing to be too worried over. If you want something that changes not to change then you will be disappointed.

It's very easy to be lost in thoughts and worries about the near future, and that leads me to a life of unhappiness.

It's not thinking-about-the-future itself that makes us unhappy, it is attachment to a certain way we want the future to be, and fear of another way the future could end up being. The unhappiness is caused by our attachment to e.g. stability, comfort etc. First thing we learn in Buddhism is to give up our attachments to our preconceived notions of how things are "supposed to be".

For me it's very hard to accept the idea that the universe is impermanent and hence I should live the present moment when I'm responsible for things to go wrong or right.

We don't have to live in the present moment, we can do our best taking care of things, planning etc. -- as long as we are not too attached to the narrow concepts of "right" and "wrong". When you look at things globally, the right and wrong are not as simple as they seem. You can have a goal in the future, as long as you fully accept 1) where you are now, what you have now, exactly and completely, and 2) that despite your efforts the future may still end up not like you wanted it.

I also feel guilty when I fell happy, because I feel I should be worried.

This probably comes from a deep-rooted preconception that you don't see looming danger, that if everything is good it means you are missing something important. This is probably just a habit you developed over years. In this case, feeling happy requires letting go of the urge to be in control, to see everything in advance.

Another component of this is probably a fear of confidently taking responsibility for the decision you will have to make. Even though it is often impossible to guarantee that our steps are perfect, we have to lean firmly on each step, so we can make the next step. This is part of what we must learn in initial ("hinayana") training, to behave like a (spiritual) warrior calmly taking charge of things.

How can I solve my problems if I'm not totally immersed in the future, thinking about all the possibilities?

In a sense, the answer is because being immersed in the future is a large part of the problem.

Buddhism doesn't recognize the things you call problems as real problems. They are conventional problems that only obtain the designation because of your own views and beliefs; in reality, whether you solve them or not is mostly meaningless.

This is because Buddhism recognizes the impermanence of life, the inevitability of death, and the cyclic nature of the universe.

286. “Here shall I live during the rains, here in winter and summer” – thus thinks the fool. He does not realize the danger (that death might intervene).

287. As a great flood carries away a sleeping village, so death seizes and carries away the man with a clinging mind, doting on his children and cattle.

-- Dhp (Buddharakkhita, trans)

Buddhism doesn't advocate the acceptance of impermanence, so much as the realization that it is the truth; once you realize it for yourself, you will give up attachment to the future and the past, since you will understand that their importance is merely circumstantial.

A good advice is to accept that reality inevitably boils down to the six senses - seeing, hearing, smelling, tasting, feeling, and thinking. No matter what comes in the future, good or bad, it will only be some combination of these six categories of experience. This is how one settles ones concern about the future and the past. Even if you are homeless, living or dying on the street, it will only be an experience, not categorically different from living in a mansion.

The closer you come to realizing this, the better, not worse, your life will become (according to Buddhism).