Oh god, this is one of my favorite themes in the world, it was very difficult to decide for just one since I don't usually have just one thing as a favorite, but I think the one I could identify with the most is Diver from NICO Touches the Walls, opening 8 of Naruto Shippuden.
I like to listen to it often and I can identify a little with this song, many times I have felt that I am in a very deep well and I can not get out, I feel I have no strength to breathe, it is very good, listen to it and if you can, look for the translation. I love to participate in this kind of things.