Why is love so hard to walk out from?

love is so so so painfull because i went through this when some one you love leaves you on day and does not even think what all you did for him at that movement you can actually feel you are heart breaking in to parts and you just start crying and when you make your mind to leave the on you loved and love someone else eve that time you mind will stop you from doing this and after that i don't know i am too stuck till here.