I agree with you, it doesn't ever "go away". It becomes a part of us, just as those joyful memories are always a part of us. Those things in our lives which caused us great sorrow remain. But...they can become bitter sweet, much depends on our preception of them. As we move away from pain and resentments, we learn valuable lessens about ourselves and our partners. We look back and instead of focusing on the painfully intense parts, we look at the good we have dug out of it. We see the growth we have acheived, we look at the strength and the courage we didn't know we had until we had to dig down deep in search of them.
Just as a childhood memory of a painful event is still within us, cradled by the child within, we have moved on, we have matured, we have learned.
True, whenever revisiting those painful memories, we re-feel the emotions which we first felt when confronted with "it", whatever the "it" happens to be. We smile and laugh at what was good/funny, we weap at what was painful/sad. BUT....it is past. It becomes a part of the rich tapestry of our life, it is only a small "thread" in what makes up the total "cloth" of our being.
It's funny that some of the most painful events can indeed become some of the most amazing beautiful "threads" in our "cloth". Bitter sweet, for sure, but we overcame, we survived what we thought at times would overwhelm us, we became stronger, better, more in touch with who we are.
Good Luck as you continue to weave your "cloth"...and what a wonderous "cloth" it will be!!!!!