English equivalent for "An ignorant child learns when it itches"

Question

In my language, there's a saying which literally translates to

"An ignorant child learns when it itches."

It's a kind of warning that means

If people refuse to realise the magnitude of a problem when there is time to solve it, they will only realize it when they're forced to deal with the repercussions.

Consider this scene I imagined.

Family goes camping; kid touches a poisonous plant ignoring parents warning; results in itchy rash on skin.

Thus, the idiom might've originated.

I found this to have a meaning somewhat close.

Learn the hard way

To learn something by experience, especially by an unpleasant experience.

But I wonder if there's a better phrase to use when warning somebody before it's too late.

Answer 1

There are two entirely different approaches here.

First, is there a literal equivalent of the saying? Sure.

The burned hand avoids the flame.

Good judgement comes from experience. Experience comes from bad judgement.

The wise man learns from someone else’s mistakes, the smart man learns from his own, but a fool will have no teacher.

Hindsight is 20/20.

Too soon old, too late smart.

As for the meaning you give,

An ounce of prevention is worth a pound of cure.

Answer 2

once bitten, twice shy

Once hurt, one is doubly cautious in the future, as in He was two days late last time, so she's not hiring him again—once bitten, twice shy. This seemingly old observation, presumably alluding to an animal biting someone, was first recorded in 1894. The American Heritage® Idioms Dictionary

Some other sayings that might be worth considering,

No man learns but by pain or shame

We learn not in/at school, but in life

What you learn to your cost you remember long (Danish saying)

Answer 3

What comes to mind for me is:

a stitch in time saves nine

which means that what you do now can reduce later hardships. It generally is a warning against procrastination rather than impending problems, however.

Similarly:

make hay while the sun shines

or

that which rests now bites later

Answer 4

I have seen various campaigns that say "ACT NOW BEFORE IT'S TOO LATE"!

However I am not sure if this is an idiom.

You can perhaps simply say it's now or never

at this time and no other

[The Free Dictionary]

For example,

Jane, if you want to get fit, then you have to cut down on the junk food exercise. It's now or never!

Answer 5

Pay now or pay later.

Didn't find a nifty explanation on the internet but did find countless examples, such as Pay Now or Pay Later: Autism Families in Crisis. The inset quote on page 11 spells it out pretty well, in applying this general idiom to an actual monetary subject:

(...) if you pay for it now, look at the return you will get on your investment. ... Or you can pay later, ... and it will cost the taxpayers a lot of money in the long run ....
– Jason Oldford, Fredericton, New Brunswick (12:32)

Answer 6

The following proverb is quite close to "an ignorant child learns when it itches":

Your best teacher is your last mistake.

As the proverb applies to past errors rather than warnings, you may caution the child by using the idiom "kick yourself", that means to be ​annoyed because you did something ​stupid or ​failed to ​act when you had an ​opportunity.

For example: Do it now! Otherwise, you ​know you’ll kick yourself if you ​forget to do it.