It completely depends on the situation. There is always a cost to a failure, whether it be time, money, and/or health.
For example:
If you're not knowledgeable about business and you spend $10,000 to start a business, it will probably fail and it would have been better to have not started a business. If you're not good at building stuff and you spend a month building a shed, it will probably collapse and it would have been better to not have built the shed. If you're not very good at skateboard tricks and you... etc
My point is that you have to consider what the probability of failure (or success if you're an optimist) is, and consider what you would lose if you fail. in such a case, it would be better to do whatever possible to decrease the probability of failure, until you're willing to risk whatever you're attempting
I'll admit that usually you have very little to lose, and it's just cowardly to not try, such as tasting new food, asking a girl out, or trying something new.
to me, the worst thing you can do is not learn from the fails of other people