Trust works like a bank account with no overdraft. Every broken promise bounces.

Reliability is cumulative and lopsided. Each kept promise adds a little, each broken one takes a lot, and once the balance is gone there is no borrowing against future good intentions. That is why small promises matter more than they seem: nobody is tracking them consciously, and everybody is tracking them. The account gets kept whether or not it is ever mentioned.

Stop making the casual commitments you are not certain about. Say you will check instead of saying yes. Then keep every single one of the smaller number you did make, including the ones that would be easy to let slide.