You shouldn't waste your effort in attempting 1 in situations when you will almost certainly fail,
Not quite. You want to consider the expected value of the attempt, not the raw probability of success. A 0.1% chance of curing cancer or 'old age' is to be preferred over an 80% chance of winning the X-Factor (particularly given that the latter applies to yourself).
It would definitely be foolish to waste effort attempting something that will certainly fail.
I agree with your qualifications, I was oversimplifying. And the reason I didn't say certainly fail because I try to avoid using the word "certain" unless I'm dealing with purely logical systems.
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