From Megan McArdle:

Life is rather too short to spend it getting angry at remote strangers.

To which I’d add: It’s also too short to spend it getting angry at petty slights, not-so-remote strangers, friends, family…

You might say, “Unfortunately, it’s impossible not to waste time getting angry.”  To which I respond: You may be unable to avoid being angry, but getting angry is much more under your control.