When you pretend to look around but you are actually looking at that person whose smile steals your heart, you define it as a crush.
Crushes are beautiful! More beautiful than affairs because:
The first one is all about that glimpse of an eye and smile. The second one relates you to the person.
Crushes have no commitment; however, affairs demand that.
Having crush at multiple people at a time is fun, having affairs with multiple people is a risky job.
Crushes give excitement, affairs come with responsibility.