Agreed. It's easy to get caught up in the bitterness of life. It's not perfect, so you can always find things to complain about. You just have to change your mentality. Instead of picking up on all the bad things that happen to you, no matter how little it is, try making a mental effort to pick up on the good things. I used to be the same way, so I made a real effort to stop and to find the little joys in life instead. Like finding a good parking spot at school (so I don't have to walk as far =D ). Just little stupid things that are good. The more you focus on the good parts of your life, especially the little things, the less you'll have to complain about!
Life is too short......but if you are feeling bitter and dont like yourslef.... then something is not right. Unhappiness will make you sick. I know. I got out of a bad job and i feel much better now and my friends think that I am like my old self again. You need to find something that you enjoy doing so you have a way to pent that frustration. You are too young to be bitter,