You cannot build trustworthiness selectively.

Trustworthiness does not partition. People notice how you treat commitments generally, and someone who is reliable with important matters and casual with small ones has taught everyone that reliability depends on your assessment of the stakes. That is a different and much weaker thing than being trustworthy.

Look at where you allow yourself to be loose: small promises, minor deadlines, low-stakes agreements. Choose one category and tighten it. It matters less than the big things in isolation and more than you think in aggregate, because it is where people form their actual estimate of you.