Well, If you want to be a disciplined person, first of all, you need to commit yourself that you are going to discipline no matter what. Do you know, what lacks in those who have no or little discipline? Nothing, else but lack of commitment. The only thing that can truly help you to become the disciplined person is commitment.
You can be disciplined by practising these things. You have to be more clear-minded, read good books, listen to good speech and podcast or videos. If you can live 24 hours of your life, that you can repeat that disciplined habit over and over again. Good Luck! Be the committed person.