Of course, you never really forget anyone, but you certainly release them. You stop allowing their history to have any meaning for you today. You let them change their haircut, let them move, let them fall in love again. And when you see this person you have let go, you realize that there is no reason to be sad. The person you knew exists somewhere, but you are separated by too much time to reach them again.
Love isn’t only love. It’s hard work, and trust, and tears, with even a few glimpses of devastation. But at the end of each day, if you can still look at the person at your side and can’t imagine anyone else you’d rather have there, the pain and heartache and the ups and downs of love are worth it.