Habits
Stop after a few losses in a row
In one line: If you lose two or three games in a row and feel frustrated, take a break.
Why
When frustrated you play worse: you decide in a hurry, talk less, take it out on teammates. Carrying on like that leads to more losses more often than to a comeback.
How to train it
Before you start playing, set a rule, for example: "after three losses in a row I stop for at least half an hour". Then keep it.