Oh, what a challenge!

This strikes me as a very difficult discipline indeed:

Complaining is the absolute worst possible thing you could do for your health or your wealth. The worst! ... For the next seven days, I challenge you not to complain at all.

-- T. Harv Eker

I venture to guess that many of us are not even aware of how often we complain. Perhaps it would be illuminating to begin by just noticing ourselves doing it!