If opportunity came disguised as temptation, one knock would be enough.
If people listened to themselves more often, they would talk less.
If reproducibility might be a problem, conduct the test only once.
If some people didn't tell you, you'd never know they'd been away on vacation.
If something is confidential, it will be left in the photocopy machine.
If something is done wrong often enough, it becomes right.
If 'success' consisted simply of not taking chances, then 'glory' would be at the disposal of the most mediocre talent.
If the assumptions are wrong, the conclusions are not likely to be very good.
If the code and the comments disagree, then both are probably wrong.
If the probability of success is not almost one, it is very near zero.