Learning to let things go is a lesson that took years. Once you realize that the only person you can change is you it lifts a huge weight off of you.
If you are not happy with something you can change it or find peace with it and let it go.
Finding peace with things that are not yours to change and letting them go will change your outlook on everything. It all starts with how you think about things.
Look for the positive in everything.
Look for the good in everyone.
Focus on the things you are thankful for.
Find a way to serve someone else.
These things will change your way of thinking.