I doubt there's one single thing that frustrates you. It's almost certainly a combination of factros, many little things that build up on eachother and just leads to a genereal sense of disatisfaction. You emntioned about getting paid, so chances are you don't like or are a tired of your current job or place of work, mostly likely your colleagues can get on your nerves (mine sure do!) and in the end you 're just in it for the paycheck which makes you regret all the time you 're putting in, doing something you don't enjoy with people you don't like, just for money.
That sounds like a pretty good reason to me for someone to be easily irratated unless chilling with friends.