Hello there, I can relate to your situation. It's VERY difficult to shake off an obsession. Depending on what the obsession is, I agree with Rainbowzz that you should put some time aside and allow yourself to obsess. If it's relatively healthy, then there's nothing wrong with it. Just make sure you don't do it in excess.

(I've actually been having issues lately with listening to music and going into my own world too much, so I'm going to try to take my own advice today! :P)