How do we unconditionally love and wish people the best?

We must train ourselves in good behavior towards what we call other people because one's self is included in the classification 'a people' and by developing a sympathetic outlook on humanity we will be changing how we treat ourselves.

One should see others as yourself and realize that if you develop cruelty it is going to affect you as well because it will color the choices you make.

One should see others as yourself and realize that if you develop compassion it is going to affect you as well because it will color the choices you make.

A person might think that there is distinction between cruelty that will affect others and that which will hurt oneself but that is mistake because the self can not be pinned down as a truth & reality and therefore the cruelty is completely unchecked in that sense.

Put yourself in the place of others and realize that they are doing exactly what you would have done given the same amount of delusion and if we punish them for it thinking 'a being is unworthy of kindness because of delusion' then we will also punish ourselves for being delusional using the same justification in mistreatment of ourselves.

Therefore if we want to succeed then we want a being to succeed and by being we mean any being whatsoever because we want to include ourselves and we are like others. There is no workaround this and otherwise one will have cognitive dissonance like 'we are all one as nature' and 'i am me and you are you, we are two', with this dissonance one will justify greed, self-sabotage, lack of discipline and all kinds of bad behaviors.

If we think our ultimate goal is xyz then it is the same for everyone else and we must strive to help ourselves to attain it also by helping others because in helping others we are helping ourselves by developing good qualities and thus strengthening the mind.

A person might treat others badly to indulge his excessive greed thinking 'another's loss is my gain' but his actions will put him in hell because he is playing a losing strategy.

It is as if a tree among trees could decide to produce fruit that kills other trees of the same kind, not realizing that it will destroy itself likewise.

Or like poisoning your own drinking water in order to hurt another and then keep drinking it yourself unwillingly because it's the only water left.

We only have one mind, it must be saturated to soak in good qualities which are pleasing to good people and only then will it invariably work for the benefit of all beings.

You are essentially training yourself & others all the time and to your best ability. Thus better you are as a trainer of others thus better you will train yourself and vice versa because your training ability depends on your faculties.

To sum up, you love others unconditionally exactly how you love yourself unconditionally but you don't have to love & tolerate bad behavior.

You should want the best for the best in you & others and be intent on the highest good.

Venerable Godatta once taught Citta the limitless release of the heart.

SN41.7:1.3: “Householder, the limitless release of the heart, and the release of the heart through nothingness, and the release of the heart through emptiness, and the signless release of the heart: do these things differ in both meaning and phrasing? Or do they mean the same thing, and differ only in the phrasing?”

Conditions are limits to the release of the heart:

SN41.7:6.2: Greed, hate, and delusion are makers of limits.

Thinking "this is mine" is a limit. Thinking "this is not mine" is limitless.

Thinking "love others" and "love myself" is limited. Thinking "spread a heart full of love to the whole world" is limitless.

SN41.7:2.2: It’s when a mendicant meditates spreading a heart full of love to one direction, and to the second, and to the third, and to the fourth. In the same way above, below, across, everywhere, all around, they spread a heart full of love to the whole world—abundant, expansive, limitless, free of enmity and ill will.

Deep down, I know there is a core that wants to love everyone for who they are. No matter who they are to me, the world, no matter how terrible of a person they are, no matter how much they make me jealous.

The only problem is, the stuff in the middle. I feel like I cannot move past things due to unclean closures to relationships and overall jealousy. I really want to wish everyone the best, but my intentions are tainted by negative emotions.

How do we break through this terrible barrier that stops us from loving ourself and everyone else, and how do we unconditionally love everyone?

Meditation practice really helps with such thoughts and worries. Samsara is already (inherently) broken. It can't be fixed. An important part of meditation practice is for the mind to see that it's not in control of how reality works. Actually the only thing we can control is our own reactions to arisen phenomena.

Fixing things is not the way to solve this. Fixing is another way of controlling and clinging to past, current and future events. If one has done others wrong it's of course a good idea to apologize and try to work things out but one shouldn't go out of ones own way to do this. It's much more important for the mind to gain clarity - seeing things clearly leads to letting go. It's not something one actively does. Letting go happens as a result of seeing clearly, i.e. to consistently see how things are subject to constant change, how they bring us suffering when we cling to them and how we cannot control thoughts, feelings etc. They arise and cease on their own.

When the mind sees that again and again it begins to let go which leads to peace, happiness and freedom which in turn leads to a more universal love and acceptance of all beings.

One can also practice Metta meditation. It can be effective but only on the surface level as it doesn't deal with the underlying problem, ie. the Latent Tendencies (Anusaya) and the Ignorance (Avijjā) in the mind.

Insight sees conceptions to be self-imposed that is to say generated by us, and not residing in the object we are seeing. We can remove this cognitive defect that since birth has misperceived conceptual characteristics as within objects themselves.

When you can observe reality closely enough to validate this you will no longer be able to generate suffering or ugly characteristics since those do not accord with reality.

Your mind is set free from these and in the absence of them there is discovered the nature of spacious luminous cognizance and are glad never to be separated from this ever again. Suffering no longer has fuel to ignite. Then you look at others and see they are exactly the same as you, engines of spacious cognizance, except they are adding a miniscule superfluous unnecessary extra activity onto it and this creates all of their samsara. But that's just 0.01% of what they are, what they actually are is that purity and cognizance with this minor fluff on top that just needs to be blown off. When you see that others are the same nature as yourself, you have a cessation of preferring some over others or yourself over them since that is not in accord with reality which you have seen. Each mind possesses the same defining characteristic of purity, and they are equal, there is no basis for preference or inequality there is just equality and a measure of who is easier to help and how.

This is pretty easy to accomplish by the way, you just need a society that's not insane surrounding itself with unfavorable circumstances. All you need is a quiet place, a couple of years with a qualified teacher and to study the following and related reasonings over and over until you approach a conclusion for or against: if a particular cow possesses the characteristic cow then no other particular object could be that characteristic. If on the other hand a collection of particular cows is required for the characteristic then you would need to perceive each particular before you could know cow, and so on there are endless reasonings.