Really the right answer is that you need to totally change your perspective on women and how we as men don't really need them.
But honestly at our age (college I'm assuming), that's a really hard thing to grasp. I even still have trouble grasping the concept, although it is very true.
In my early school years the way I avoided one-itis is by giving myself an excuse to avoid it.
In other words, if I really liked a girl then I would PURPOSEFULLY avoid caring about her in an emotional way. While this is a fake method of hiding your one-itis, if done for awhile it DOES fool your brain into getting rid of it.
I've had many GFs that started as one-itis. By using willpower and avoiding my emotions to these women, I successfully landed these women THIS way. They were turned on because I was not needy. The funny thing is, once they started becoming emotionally attached to me, I was becoming emotionally DETACHED to these women in reality.
Once you have done this several times and see that your oneitis is just based on the fact that you want her and she doesn't want you, then you will eventually realize that one-itis is fake. It's just infatuation built up in our heads. No woman is good enough to dedicate the majority of your day to.