You will move on by readjusting to your life. The memories will alway someday comeback every once in awhile. The current moment you feel today will fade away.

Honestly, I think it's different for everyone. I'm also not sure you can "just let go." It's easier said than done, for sure. Not knowing your particular situation it's hard to tell you exactly how, but just recognize that you can do it a little every day, and don't beat yourself up on the days you can't. Grief is a long process for many, and it's going to take time and patience.