When things are bothering you it can be hard to not let things bother you.
It can take some time to get over things and not allow things to bother you.
You have to learn to block things out of your life that are bad such as bad people or toxic people who may seem like your friends but then they turn their back on you.
If you have someone that is bothering you then you need to stand up to the person and let them know that you're not gonna take it from them.
Then brush them off and ignore them.
If you have things bothering you then try to get away from the house, state, town etc you're in and go see some new scenery as that always helps me.
I try to take a road trip out of state at least once or twice per month even for a week or a few days.
Seeing new scenery and getting away helps clear my mind of negative thoughts.
Basically all you can do is to learn to brush things off and avoid thinking about it.
Doing so can be hard but as time goes on you can usually learn to not even think about those bad things.