I try to gauge situations by thinking "in x amount of time, how much will this situation effect me?"
So, i have a bad day and lose lots of money. I think, in 24 hours, how much will this sting? In a week, will i even care? In 2 months, will I even remember?
If you are a profitable trader, a big loss doesnt mean you lose money, it means you lose time. Positive expectancy will always make you new money, but it will take longer to get to where you want to be.
After i calm down, i go back over what happened and attempt to not repeat that set of decisions. (this isnt always clear, and doesnt always work though, of course)