It's funny though because you only need a short amount of discipline. Because after you use discipline for a while, it just gets way easier as it becomes a habit. Reminds me of this great Bojack Horseman clip - https://www.youtube.com/watch?v=R2_Mn-qRKjA

Years and years ago I started training seriously for a triathlon. Then a half ironman. Then a marathon, and after 2-3 years of having a few races a year on the calendar, I just started exercising every day. At the start, a lot of the days took discipline/motivation to get out the door. After a while, it was just a few days of discipline a week. Then a few days a month, then a few days a year. Now it's automatic, and something I actually look forward to rather than dread (obviously in a hard training cycle there are some sessions I dread, but it's almost like my brain turns off and my body subconsciously gets my stuff and gets me out the door).

The longer you do something the easier it is.