Saying things like "Sorry, I don't have time to talk right now" or "I can't come because I have somewhere else I need to be then" and so on. Sparing myself from the discomfort of telling the truth or alternatively thinking I'm sparing people from feeling bad by not telling them what I actually think as if I was somehow a better judge of their capability to handle truth and discomfort.

And I'm not referring to radical honesty - I'm talking about simply not saying things that are untrue.