I don't know that this is true in your case but I've seen guys who become more interested, or who don't lose interest as fast, when they discover a girl is less available.
In many of those cases I think fear is a major part of the problem. Can't screw up what can't be so it remains perfect, and they remain perfectly miserable, but don't have to take responsibility because the women are unavailable.
Casually associating with women who aren't what you are really interested in can alleviate the fear.
Unfortunately, I have seen some of the guys settle way, way, way below their potential and others marry the first girl they try to associate casually with.
Ultimately, if fear is part of the problem the long term answer is to deal with it directly, then try associating with eyes wide open.