Frustrated

How mummies with more than 1 kids handle your emotions and mood? I gets easily frustrated and annoy by the slightest sound or whining and misbehaving. It started when I’m pregnant with my #2, at first I thought it’s my hormones but it doesn’t go away after I give birth. I find myself yelling and throw tantrums at my #1 for all the little things. I tried to control and take a step back and breathe but it doesn’t helps. How you guys handle such situations?