Be a man of your words!
When a person promises something and didn’t deliver at the end, what would we think of the person?
If the person really put in a lot of effort but just that he didn’t have the luck to get it done, then he can be forgiven and be trusted for the next time. But if he didn’t take it seriously and slack all the time and we somehow predicted what would happen, then he doesn’t worth our trust anymore.
Your words and your actions will build other people faith and trust in the words that you speak. So, when you openly pronounce with your words that you’re going to do something, then you should follow suit and backing up your words with serious action. The pattern of being a person who doesn’t back up their words will become incredibly noticeable as to being a liar and he will lose the people faith and trust.
Trust is something very hard to regain once you lose it.