Discipline is what helps us achieve our goals, without discipline we can't succeed in most cases but even discipline in not of just one type. Most of us live a disciplined life but what's the reason of our discipline defines what we achieve in life. If we discipline self, we can achieve every single target but if we're disciplined by others, you will only achieve what others want you to. Hardly 1% people will teach you discipline for your good, rest of them will want you to be in discipline as long as you're doing something for them, after that they don't care. Now, these types of differentiation are not easy, so just get to the bottom-line, either you discipline yourself or your personal life is certainly ruined, you may succeed professionally as you'll be disciplined by others for that by force of enticement, threat, force etc. But that will give you a wrong message and that message will be "Discipline is bad, and I should stay away from it", never ever, make that mistake. Discipline is always good for you and the best type of discipline is self discipline.
Now the question arises, how to do it?
Well, first of all you you need a VISION, where to go, the direction in which you should focus and put your efforts in. After that a PLAN, one that will take you towards your goal, after that you need a contingency plan (Plans fail, we must have a backup), and now the last step is, FOLLOW THE PLAN AT ALL COST. Do it and you will never be away from discipline and it will become an inseparable part of your life.