Is it wrong that I'm going to tell my friend he needs to stop feeling sorry for himself?
Why do you want to tell him that?
He's just had a piss poor attitude lately because of it.
Being frustrated with his attitude is pretty normal but you shouldn't tell him that. If he's going through some problems that are making him feel down you should be trying to help instead of being rude.
I disagree.
Telling a friend to stop feeling sorry for himself is rude. It makes you sound insensitive and apathetic.