I agree, never make big decisions right away. Give yourself a time limit that you must wait. "I must wait this many days before I make a purchase of this many dollars or more." And you have to stick to it.

Sleep is very, very important and so is exercise, diet, and being on a routine. Routine is especially important when you mood goes too low or high because as creatures of habit, being off your routine will make you feel uncomfortable and you'll want to get back to it. This is one that helps me a ton.

Do you use a mood tracker? Sometimes if you track your moods and start to pick up on patterns it helps you pinpoint what's going on. I try to track my moods and triggers for at least one week per month, it's amazing what i learned from doing it.