The best thing you can do is develop habits that help you recover at every timescale. On the smallest timescale the Pomodoro Technique is really, really good at least in part because it quickly proves you wrong if you think you shouldn't stop because "momentum". Never, not once in using the technique, have I ever lost momentum and in fact quite often I come back to the problem with much greater clarity and speed. (Note that taking a 5 minute break every 25 minutes is entirely different than taking a meeting or working on another problem. Those are context switches and are the worst of all worlds - you're not working on the problem AND you're not resting.)
On the daily timescale, morning meditation serves the same purpose as the 5 minute break, but it's more intense and more holistic. I see it as giving you "headroom" for your day so you can deal with things as they come, with equanimity. My worst days have always been the ones where I stubbornly refused to meditate (and I often do that because I have been meditating regularly and feel like I don't need it anymore. Ha. My mind is sometimes a real dick.)