Is there an idiom or a proverb meaning 'if you don't know how to do something, then don't start doing it in the first place?'

Your friend accepts to do a research project for someone but he doesn't know how statistics works. He asks you to help him out. You want to say something like 'If you don't know how to fly, then don't jump off the cliff.'

My best find up to now is 'If you can't stand the heat, get out of the kitchen' but it doesn't imply knowing or not knowing something. It's more about persistence or tolerance.

1 Answer 1


Fools rush in where angels fear to tread.

Fools don't realize that something may be a lot more complicated than they think it is. This is a general statement, and in that respect it is unlike your "Don't jump off the cliff if you don't know how to fly." which is said directly to the person about to fail.

Another possibility is:

Don't bite off more than you can chew.

It means don't take on more than you're capable of doing.

If you can't swim, don't jump in.

That's not a proverb, but it resembles one.

  • Isn't it about dangerous situations? I feel it's a bit strong. Would you (as a native speaker) say that? It's a question just out of curiosity: Let's say you didn't want to use a proverb, how would you naturally say it to mean that?
    – Yuri
    Jul 10, 2017 at 18:27
  • No, not only dangerous situations. It also applies to situations where the "fool" will quickly be in over his head with difficulties or complexities he did not expect.
    – TimR
    Jul 10, 2017 at 18:40
  • Your saying has a sarcastic bite to it (can't fly, don't jump). It seems you're looking for a general purpose pithy saying. If you can't stand heights, don't ride the ferris wheel. But with a special focus on ability or skill.
    – TimR
    Jul 10, 2017 at 18:43
  • 1
    Yea I would include that in my answer. I'm looking for something like 'If you don't know how to fix a car, don't open a repair shop'. You know something like this. +1
    – Yuri
    Jul 10, 2017 at 18:49
  • 2
    "Do not undertake vast projects with half-vast plans." I know it's not a perfect fit, but I like it so much that I can't resist typing it. Jul 10, 2017 at 22:41

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