When talking about the word discipline, i think some people r misunderstanding this, discipline you should have in your way of playing, dont get out of your statutes and own rules (dont start doing things that usually dont do before, there are excesses but you should not do too many ), some people start a game regime as an olympic sport and really that path i think isnt the right one, the body and mind should be in harmony and perfectly rested, if you can add more rest it is much better .. just make comparisons of playing 24 hours straight without sleeping, and playing 5 hours sleeping, hydrating and eating perfectly .. the less you saturate your mind the better your results will be .. unless you are forced to do so and if that were the case you should take 1 day or 2 days to rest.
if you ask me today: are you disciplined as a player? and i would say that my discipline is basically dont stop playing poker more than 24 hours .. keep me so active that i have to find another game to clear my mind for 1 day or 2. I usually recommend playing 5 or 6 days a week, and no more than 8 hours. Also, is important for me to play listening to good music