You fall in love and care for the person. You do your best to show your concern, trying to be constantly consistent as possible. After some time, you'd disappointingly realize things. Somewhat some way he detached and sends signal to leave him alone and let him do what he wants, even if it was initially mutual that it’s against your principles. You get tired. You get tired of being upset every time, that you just let go. To relive your drama, you let go; to help yourself from drowning to a person who, you realized, is unwilling to cooperate in the long run... You simply let go of your grasp and let it be.