You don’t know a language, you live it. You don’t learn a language, you get used to it.

It’s a good quatation.
The main point - not to transfer the rules and structures of your native language to a new language, but to get accustomed to new structures, to start to ‘live’ in a new logic and a new culture.

Reminds me of Nelson Mandela’s famous quote:
‘If you talk to a man in a language he understands, that goes to his head. If you talk to him in his language, that goes to his heart.’