I do also have this from time to time, but not very often. It does not occur to me when I have things to do that are meaningful to me. Like working on a cool

I do also have this from time to time, but not very often. It does not occur to me when I have things to do that are meaningful to me. Like working on a cool hobby project, having fun with friends, thinking that my work is fun. Maybe your life is really boring right now, so you have reason to be frustrated. This is good, isn't it? This probably means you need to change something. Obviously what you do, but maybe also your attitude. You should rather look forward and think what you can do and not what you could have done. Not sure what you are interested in, maybe you want to go rafting, learn climbing, learn Vietnamese, learn to cook food that others can eat, create a funny website, go to another country, go to the Military, run like Forest Gump through the US, or maybe walk through the US... So much stuff to do. Also stop whining, maybe you need to watch some more Clint Eastwood movies. And in addition some documentaries about refugees in Africa or child soldiers. Afterwards you feel more sorry for them than for you. What also helps, talking a cold shower in the morning (or hot-cold ;)), making some push-ups, eating breakfast. You'll feel much more vital afterwards. (Speaking from experience.) Anyway: stop comparing yourself with others and don't forget that they paid a price for being so disciplined.