There is a study that proves the negative effect of sleeping while in a state of anger. Before I’ve known about the study, I’m already practicing the habit that I call as never-go-to-sleep-angry method. Before I go to bed, I leave unwanted feelings by relaxing first like controlling my breathing or taking a bath, then I tell myself some comforting statements like these:
“They just don’t understand me.”
“To be great is to be misunderstood.”
“To understand all is to forgive all.”
And a lot more. For as long as the words are comforting to me, it doesn’t really matter if they don’t fit in the context why I became angry.
You can only do that if you have forgiven yourself first. Never go to bed with a heavy heart. Cast them away first and leave them behind. Forgive yourself and others as well before going to sleep.