Get caught in one lie and suddenly your true stories need proof.

Trust works as a default, and the whole value of it is that nobody checks. One discovered lie switches the default off, and then the honest things you say start arriving with a question attached. Rebuilding is slow because it has to be done with evidence rather than words. That is the part people underestimate when they weigh a convenient lie.

If you are in that position with someone, stop asking to be believed and start being easy to verify: the receipt, the location, the thing done when you said. Months of small confirmations will do what no explanation can. If you are not, notice what you would be risking.