Want and wish English

British people sometimes say `you don’t want to do that’, but this isn’t good English and it can be confusing. It probably seems to mean that you don’t wish to do that, that you have no wish to do something. This might seem as if they are telling you what to do.
But in fact they are not telling you what to wish for, and they are not telling you what to do.
They are advising you not to do something, they are telling you that it is not a good idea to do it. They are not telling you what to do, they are trying to help you.
If this isn’t good English, what is the correct way of saying it, what is the correct way of advising someone not to do something?
Probably the most polite way of doing it is to say `are you sure you want to do that?’ This is good English.
In colloqual English – the way most British people actually speak, hardly anyone says `I wish to do something.’ It’s too formal. Instead, they’ll say `I want to do something’, ie. `I want to take a holiday’, or `I want to learn to swim’, etc.
They only time they will use `wish’ is like this: `I wish I could do something’, ie. `I wish I could take a holiday’, `I wish I could learn to swim’ etc.
Really, `want’ means that you can do something, that it’s possible. `Wish’ means that you can’t do something, that it’s impossible – or nearly impossible.
When someone says `I want to take a holiday’, it’s possible, they could  take a holiday. When they say `I wish I could take a holiday’ they are saying that it’s impossible.