Momentum: All or Nothing

Why is it that, in order to be productive, I need to already be getting something done? If there's a list of things to do at home, I can't miss a beat after work - I'm good as long as I just keep going. But if I sit down just for a bit it will most likely be all evening. It's either 90 miles an hour or no miles an hour at all.

I know I'm not the only person this happens to. An object in motion stays in motion, right? (and we all know this philosophy applies to workouts too) I would just love a little bit of balance - the motivation to get a nice,  happy-medium amount of things done with some time to relax.

Part of me is inclined to go overboard and plan it. I know there are some obsessive planners out there, but scheduling all parts of my seems a little overkill. Le sigh.