I have been there myself, and looking back I found myself wishing I still had a bike I sold. If its not hurting you to keep it, my advice is to keep it if you truly enjoy THAT bike. If its just a bike, and we've all had one or two of those, then only you know what's best for ya. But regret is worse than thoughts of what if. You can talk yourself out of the "what if.." thoughts, but you can't undo something you regret. Either way, good luck with whatever decision you come to. And with school.