For me there are two types of crushes: romantic and platonic. Romantic crushes are hard. I guess that is why they are called that. Because chances are your feelings are going to get crushed by the object of your affection at some point or another. Generally, for me, my crush never knows that I am crushing on them and so they have no real care for the small slights to my emotions. But that is how it goes. I have had many romantic crushes so far in my lifetime, none of which resulted in a relationship of any kind. Thinking back to high school I can say with a fair amount of certainty that there were several guys who probably had crushes on me. But I was one of those unaware teenagers and so I never realized it. There was a very cute football player who asked me to tutor him in physics but I stupidity admitted to being mediocre in physics and said no. I think back to my high school self and want to slap her. Oh well. Nothing to be done about it now.
Platonic crushes usually come with new friendships. For me, when I make a new friend, I get a little wrapped up in that person. Because it is exciting. Here's a new person to get to know and find out all the things about it and it is fun. But eventually the newness wears off and then you are old friends and it is comfortable. This is much like any new relationship now that I think about it. Once again, in high school and college especially, I tended to have a lot of platonic crushes. Usually on people that I wanted to be friends with but never made the extra step to have an actual friendship. I was usually the "pet" of the older students because I was shy and nice and quiet and they found that adorable.
But now that I'm older and married, I don't usually think of things in that way. Do I still get crushes? I would say yes, but I'm less likely to admit to it. Because there is that thing in society that says no, I shouldn't because I am married and betrayal, blah blah blah. But crushes are not necessarily about sex. It's about finding someone else interesting. And, like all relationship, it's about establishing the boundaries that are okay for your stage of life.