I think that as everyone gets older, it becomes easier for us to let negative things go. We do not stress as much about what people think of us, we aren't as hard on ourselves on mistakes, it takes less time to forgive or forget slights, and we may even begin to shrug at some misfortunes.
I know that I feel this way now, and I can say that it is quite a relief to let go. Many negative things in life are only as powerful as we let them be. We create monsters out of those negative things, and give them their power. We do this a lot when we are children, and we continue to do this the rest of our lives. What we don't have to do, is make so many monsters.
It's simple, but it's not easy. I think that every individual's path to understanding how to let things go is different. Mine for example, was purged in my youth. Other kids at school were very hard on me, and I was harder on myself still. I was very self-conscious, and though I was strong academically, I spent more of my time worrying about trying to get other kids to like me at school than anything else. I found something to fear in many aspects of my day-to-day existence: That I wasn't good enough at a sport, that I looked like a dork, that someone would push me around in the hallways, that my family was poor, that my artwork would get too much praise from the teacher, that someone would call me names, that I would sound too smart in class, that people would make fun of where I lived and the cars my parents drove, that I didn't wear the coolest clothes, that my handwriting was bad, that I was Catholic, that I had Jewish heritage, that... All of the things that were me, that identified who I was, I tried to hide and pretend weren't there. I couldn't let go of caring about all of those things, and it made a lot of my childhood miserable.
Now I'm not complaining about my youth, I loved much of it, and was blessed with more than I ever could deserve. What I didn't have was the ability to let go. It was unfortunate that I went to a small town school; I didn't have friends that supported me and I wasn't comfortable letting myself open to identifying with anyone for fear of being made fun of. I taught myself well to hide. I pulled all of those monsters around with me on a tight chain, and hid them. Perhaps in a way I built fake monsters by not being myself: I tried to wear the clothes the other kid did, I kept quiet when I knew answers, I made excuses to avoid playing sports, I hid during recess and open class periods, I made my parents pick me up late or from distant locations to avoid being seen, I tried and failed to make fun of other kids...
Instead of letting go, I defied the world and myself! When I look back at that time now, I am floored with how stressed I was as a kid. I'd like to go back to that little boy now and tell him that it will all be okay. That none of "this" matters as much as he thinks it does. That he is only creating and building up monsters. But maybe that visit to the past would be a mistake. I am very proud of myself with how I handle stress now by letting things go, and maybe it took all of that practice as a child fighting monsters to get here.