Where is your focus?
Keep in mind that if something/someone is bothering you, it can be an aspect of yourself! For example if you get annoyed because someone else always claims to know best , it can be helpful to ask yourself, “Am I also a bit like that?”.
If someone has done something to you that you are bothered about, something that you are thinking about often (it’s unfinished), then you should consider whether you can make a closure in any way.
Do you have your focus on the good things around you/in you, or do you have your focus on things that disturbs you? In the end it is a choice, where do you choose to have your focus?
Giving to much power to external petty things makes you powerless.