As most on an Internet forum, shy/social awkwardness is the main one, I'm far more adept at this than I was in school, I can actually talk to people (women in particular) now without coming across as the strangest person that just blushes and can talk for about 10 secs before awkward silence kicks in.
Procrastination, I'm so laid back sometimes I have to force myself to do something or it just won't happen, it annoys me when I think about it.
Anxiety. Goes hand in hand with being shy, I get anxious over the most stupid things with no real reason for it.
Like someone else said, genetics. A couple of long term health conditions make life a little more frustrating, which they say is probably genetically linked so yeah, that's annoying.