Deep breaths are the best at releasing stress. Pay attention to your shoulders. Are you "wearing them as earrings:??" Make sure to keep your shoulders down where they belong. And just plain don't over-do it. Which is often the hardest one of all.

Three year olds are the hardest, I feel your pain there! On that all you can do is be firm, set limits, and don't crack (give in) no matter how much you want to. That said, saying no all the time doesn't work either. So pick your battles. Ask yourself if its worth the fight before you get into it. Keep her busy, so she has less to get into it with you about. Do you have a way to get her out of the house?

Good luck!