If you tell the truth, you don't have to remember anything.
/Mark Twain
In other words, you can't get caught in a lie if you are always up front. No stress.
Learn how to use words diplomatically so that you can be respectful and kind while delivering bad news (because being honest often means telling people what they don't want to hear).
Here's another quote on Truth:
If you shut up truth and bury it under the ground, it will but grow, and gather to itself such explosive power that the day it bursts it will blow up everything in its way. Emile Zola