I think that it is the most beautiful dream one can have. Nothing beats dreaming about the person u are inlove with, its on a level in its own.
hw and why it happens? I do not know bt wht I do knw is that it is an Amazing feeling. You tend to wake up in a liminal state and see the person right infront of u. If that doesn't make one smile and have a good day, I don't know what will. 
But if you only like that person because you can't stop thinking about him/her then no. A lot of
the times it is just our stupid brain messing with us when someone is really not worth our time!

I know it's just a crush. It keeps me going everyday! - lovebug-
I know it's just a crush. It keeps me going everyday! -lovebug-