Did you ever fall for someone you know you shouldn't? Try hard to hide your feelings, but it's so hard you just couldn't? He's or She's only a friend, and can be nothing else. That's the lie you keeping telling yourself. You are so happy when in his/her presence, But keep reminding yourself it could never happen. A simple meet of the eyes turns into a stare. You hide your feelings so no one can see. You don't want to tell your friends because you would get embarresed.
So you keep your feelings bottled up and tell nobody.