I constantly obsess over things i have done, or heard others comment about something i thought pertained to me. It turns out to be something i just can't shake for a while, or get out of my head. Usually it pases with time, but sometimes comes back and starts all over again. Eventually it will escape my head for good and not bother me anymore. Time seems to be the only advice i can give you though. Something else will eventually distract you from it, and it can take over your thoughts.