Parents, what do you do when you feel like you want to explode because your child is too hard headed?

I've seen my cousin (who has a toddler right now) take really deep breaths whenever she is having a hard time in dealing with with her toddler. Sometimes, she asks me to look after my nephew for a couple of minutes just to 'meditate' and to 'calm down'. I always ask this everytime she comes back smiling again: What did you do? And she always say in response: Thought of happy moments and happier moments to come as Niko (her son) continue to grow healthy and lovely as he always been