Not gonna lie, I had 4 one-itis's so far LOL.. I ended up getting the last 3, the first one I never slept with 'cause I moved away to a different state shortly thereafter. She just recently added me on facebook and she is married with kids and not nearly as good looking as she used to be, (funny how that makes things better lol).
The last 3 that I actually did end up sleeping with, I ALWAYSSSS felt a whole lot better after sleeping with them and eventually lost the one-itis. I think after you sleep with a girl you had a one-itis for, and you really nail her good, you eventually lose the one-itis shortly after that. One-itis is something you should try to stay away from obviously, as it puts undue pressure on the situation and actually makes you less likely to get the chick. It's weird how they happen though, always unexpected, and the last one especially took me off guard since by this time I was well known as a master player. But there always comes that one that kinda "gets you" I guess lol and you fall under the terrible one-itis spell. One thing that definitely helped me is that at least I KNOW that I CAN love other girls, as the first one-itis you think "i'll never be able to find another girl like this". and then when you do it's like "what the heck was I thinking", after a couple of them though, you realize taht this is a temporary feelign and that NO MATTER what happens, you WILL find another girl that you like just as much.