Wah How to use Impersonal You / One.

We can use you to refer to people in general.
In these sentences, you doesn't mean one person. 

• You can't believe everything you watch on the television. (People can't believe everything  they watch on the television.)
• You should always be polite. (People should always be polite.)
• You can’t learn a language in two weeks. (People can’t learn a language in two weeks.)
• If you get ill, you should see a doctor.
• If you want to succeed, you should work hard.
• The only place you can get great food is in Thailand.

In formal English, we can use one instead of you.

• One can't believe everything one watches on the television.
• One should always be polite.
• One can’t learn a language in two weeks.
• If one gets ill, one should see a doctor.
• If one wants to succeed, one should work hard.
• The only place one can get great food is in Thailand.

If one fails, then one must try harder next time.