I think that the memories we have intact in our minds are a reminder of our past, be it good or bad, they remain experiences we’ve had, helped made possible by different people in our lives, regardless temporary or permanent. It would be a positively inexplicable feeling to gain–from losing a bitter memory–except the maturity you’ve obtained would be lost with it. In the end, you stay stagnant as a human being, without memories to carry you, aid you to growth in terms of your soul, no matter what age you’re at.
Looking back at those memories in your head, whether it haunts you, mortifies you, or made you smile, they’re there for a reason unbeknownst to us. We have to trust God for that. The feelings that rush back to you upon reflecting on a memory might make a big impact on you in terms of how you behave or react, but if you think about it, every thought you have, it’s inside your head. Yours and no one else’s.