Ways to bite your tongue (read with sarcasm).

When you can only think of, "too honest it may or will have negative results," things to say.
  1. Repeat what they say in a tone that sounds concerned or questioning the words as if you feel perplexed.
    This causes them to continue speaking because they probably don't care what you have to say about what they are talking about.
  2. Just nod in a way you know seems acceptable in context to their situation.
    It shows you're listening. Even if you want to check out with truthful comments.
  3. Make comments about them being in their situation, never compare their situation to anything related.
    Use the word "you" and never "I"
  4. Take what pops in your head to say and analysis it.
    How would you feel, does it seem rude, do you care, is it important, how would they take it, can you say it without tone or sarcasm, etc.. All in second.
  5. White lies and compliments are the norm.
    Again no one really wants true honesty.