M. Scott Peck wrote the best definition of love I ever found:

“Love is the will to extend one’s self for the purpose of nurturing one’s own or another’s spiritual growth… Love is as love does. Love is an act of will — namely, both an intention and an action. Will also implies choice. We do not have to love. We choose to love.”

If you truly love someone, regardless of where the relationship goes, your desire for their happiness and growth won’t ever change. But that doesn’t mean you won’t feel grief or loss.