Many people mistake lust/infatuation with love. They think they're in love but it's really infatuation or lust.

Thats why so many relationships end. The initial spark only lasts so long. Once it does they think that something is wrong with the other or they dont love them anymore. But it's merely that they're not infatuated with them anymore.

If they were truly in love that love would keep them together. They wouldnt part just because the stupid, "teehee I am crushing on him" feeling disappeared.