If you're not the type who's inclined to acknowledge, analyze, consider, and accept your own embarrassing flaws, bad decisions, misdoings, selfishness, and biased perceptions of events and ideas, then your opinions, judgments, and conclusions in concern to anything else should always be taken with a grain of salt, I think.
After all, we're all driven by pride, vanity, emotion-based decisions, impulsive choices, biases, and a fear of looking dumb, wrong, small, and/or too weak to do and say what we feel is right above what we want to be true or what we impulsively desire in any particular moment. It's human nature. And we all cave into these things more often than not.
The key to being trustworthy is to have the willpower and humility to admit when it happens instead of tricking ourselves into rationalizing how we were in the right all along. Because it's okay to be wrong, bad, and weak. We're all wrong, bad, and weak. People don't trust you or your word because they know you're always good, right, and moral. They trust you because they know you don't lie to us and yourself when you're not.