I think that for a lot of us, there is a fine line between obsession and dedication to doing a task fully and completely.
I have had behaviours that produced no good ... sitting with a set of encyclopedias looking for something for hours on end, seeing how many harlequins I could read in one day etc. I also have become immersed in diet message boards and fitday and planning weight loss and exercise. Any of these to the detriment of my family life and things that need to be done.
When I'm feeling really good I can carefully balance maybe two projects, family and work. Right now, I'm redecorating our new home and trying to get back into exercising and eating right. All the while still trying to work and feed my family. Yesterday I spent waaaay too much time downloading music
It often takes written goals and determination to leave one thing and move on in time.
The problem with what we normally think of as "obsession", seems to be that component of doing "no good". There also is the component of harm.
If we can substitute one obsession for another ... I believe we can work at it until we've substituted a couple of dedications for those harmful behaviours.