Promised my boy a holiday. Found out that now he's 2 Ive got to pay for full wack for his flights. Because he's my boy he get's his holiday and my crediters get excuses.
My parents have grilled me about saying "I promise" for as long as I can remember. I too never say it, unless it's a sort of joke/casual banter, like "I promise I won't bite you if you come closer".
I too stick with "I will try my best", so you're not alone in acting this way.