Become more disciplined than your last difficult season.

You have already been through a hard stretch and you know how you behaved in it, including where you slipped. That gives you an unusually specific target: not discipline in general, but the particular way yours failed last time. Vague resolutions have nothing to grip.

Recall the last difficult period and name the exact thing that went first. Sleep, the work, honesty with people. Prepare a plan for that one thing before the next hard stretch, and you will have made real progress.