Giving my power away...

This has become something I am pretty good at in my adult life. I feel like I let people dictated way too much. Mr. Workin' can wreck me with a look. The moms at school, the kiddos, and my family can also say next to nothing and it causes me to unravel. I ALLOW this to happen by not believing in myself enough. If I am questioned by my spouse it cuts me. Are there things you tell yourself that help you ward off these hurts? How do you make the voice in your head be the loudest one you hear?