The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

Their DISCIPLINE
and loyalty are absolute.
Game of Thrones Season 3, Episode 1

You didn't get much DISCIPLINE
as a child, did you?
Game of Thrones Season 6, Episode 4

No DISCIPLINE. No training.
Game of Thrones Season 4, Episode 9

You don't have the DISCIPLINE.
Game of Thrones Season 3, Episode 7

Perhaps you need more scribing work
to DISCIPLINE your mind.
Game of Thrones Season 7, Episode 5