Note: Being irritates always doesn't mean it pisses you off, it just means it's grates on your mind, and it's usually some sort of pet peeve or it can be something that leads TO YOU getting very angry but not the thing that does it. Though it can also just be a total berserk button.
This is not about big life problems, quite the opposite.
Thing that irritates me more then anything on this planet: Knowing that recognize a reference but can't at all place it. For instance you hear a piece of music you know you've heard before but can't pin down where you've heard it from. This often leads me to go on extreme hunts for the reference I'm looking for and often frantic if I can't find it.