finding somebody really attractive but you don't want to fuck them, aka lack of pheremone correspondence

It's fun having beautiful women as friends without the primal instinct to bed them.

sounds like you're either hung up on the ex a little, or you have the age-and-experience thing going where you think you can see where things could lead and you think you're preemptively dodging something.

I think definite good things take effort to get rolling, but not all things you've invested effort in turn out to be good, if that makes any sense. So it's good to try things, even if it's just talking to an attractive woman and getting to know her.