I do not know if you have to let it go. You have to let go of how it affects you. People grieve in different ways and for different lengths of time. I lost my dad suddenly when I was 24. Theres a whole history behind my relationship with him but I got through in Id say less time than expected and now when I think about him I feel a bittersweet feeling. Almost like missing what could have been and accepting what it is now.