I think the point of "do X every day" is getting over the physiological hurdle of starting something. If you want to write more but find yourself watching TV a

I think the point of "do X every day" is getting over the physiological hurdle of starting something. If you want to write more but find yourself watching TV all evening because you fell burnt out from working all day. Maybe you should be relaxing in front of the TV, but you are in a better position to make that decision once you have force your self to get over the initial hurdle by writing n words. That n should be sufficiently small that if if are burnt out and want to back to relaxing you have not overly burdened yourself, but you will likely find many occasions when you want to keep writing because its something you would rather do than watch TV.