Following a habit protocol when desire isn’t there.

I’m using the drink plan tools to change my habit of watching TV in the evenings. I make my plans 24 hours in advance (e.g., tomorrow I’ll watch 1 hour of my shows), but sometimes when the evening rolls around I don’t feel like watching the full hour of shows or even turning on the TV at all. Should I watch the full hour anyway because it’s part of my plan, even though I don’t have desire in the moment? If so, why?