Figure out what triggers you to stop being disciplined, and try to see if there's a more intelligent solution than simply telling yourself you won't make that mistake and applying willpower.
For me, when I see chop markets, especially after 11, no matter how hard I try to sit through it and wait fro real movement, I 95% of the time churn. So now, when I feel the markets start to die down, it only takes one small loser, or even a possibility of me thinking of taking a shot when I shouldn't, to walk away.
I also get killed by a few huge down days on the month, and the pain of telling myself I won't do that, limiting my losses for 6 weeks, then blowing a month's worth of profits in one bad day from a few trades... it made me realize, the only way to ensure I dont' lose big is to have software cut me off from trading and to kick me out of my position if my open P/L exceeds 1/2 my daily max loss. Even if I get shitty market fills and am every so often forced to panic, it's well worth it.
Just what has worked for me.