Since the opposite sex is never the active party, it's very easy for a man to get infatuated with anyone who gives him time of day. Takes a certain amount of experience to distinguish friendliness from romantic interest. To state the obvious , you're living out these fantasy relationships as kind of proxy for the real thing.
Eventually things change. Crushes become a serious threat to your mental health as you age. The mind goes into a kind of self-preservation mode. Assuming you're not just a late bloomer eventually you'll get to that point where it become less frequent, less intense. My only advice is to develop more friendships with women and get used to being around them as acquaintances and friends.