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Old Advice

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"If you don't have anything nice to say, don't say anything at all."
I know this advice has been around the block, but it still holds. Don't be cranky towards everyone else just because you'll never see that jerk who made you spill your coffee ever again.
If it's not their fault, don't take it out on them.
If it was the jerk, however, I guess... just don't embarrass yourself. They could be having a bad day too.