There are a multitude of reasons to feel as if you don't belong in life. Perhaps your reactions to given situations don't match those of other people one hundred percent of the time. Maybe words keep getting thrown at you, one major one I can think of is 'should'.
I'll use it in partial sentences: You should want to, Should you be, and Shouldn't that be...
Others I cringe at: always and never...
It's my theory/opinion that most of us grow up building a map in our heads of how the world should be. We human beings build rules to suit our own observations of the world around us and gather comfort from them. Not only that but we are subject to the views and rules of our parents, relatives and what we perceive in society.
The older I become the more these rules don't matter. For me at least, they've only served as a constant reminder of failure. If you let go of the map in your head and dare to do things your own way, yes you will meet resistance, but change is inevitable. Live your own way and you might find being true to yourself is far more satisfying than shaving the corners away to fit in a round hole.
Does that mean I promote anarchy? Nope. Does this mean I don't have morals or ethics? No. If those are the only questions you've asked yourself while reading this then you aren't ready to let go of the map and you may not ever. (I almost wrote never there.)
So, to the other oddballs and misfits out there: I salute you!