A lot of people walk this earth not being satisfied with their lives. It is true, that many people are born into harsh surroundings, poor families or born with disabilities. The problem is that usually these people do not consider this situation fair and they become deeply frustrated with life.
Let me tell you that how you perceive life depends only on you and your perspective. Let me tell you why. If you whine all the time about how hard life is, you simply create a mindset for yourself where everything is hard, you cannot achieve anything. This is not science or some study, this is simple logic. It comes from repetition. If you repeat something long enough, you will learn it. This is how humans and animals learn.
So, if you just whine, life will suck. But what if you sat back a bit and thought about life a bit different. Let me put it this way: you were born into a beautiful playground where you can test your limits and can play as much as you want. How you play is up to you. No matter what you do, no matter where you arrive, you are simply here to play.
If you view life from this angle, you will realize that life is not hard at all. You can do anything you want. If you want goals that are hard to achieve, the play will be harder, but it is still just a game.
We are here on this beautiful playground to live and play happily regardless of the circumstances we were born into. Everything is possible and the thing you can do, infinite. So just play along and enjoy life while you are here.