Ernest Hemingway, one of the most prolific American authors, had a habit of routinely leaving his work unfinished each night before bed. He would just stop writing mid-chapter, mid-paragraph, and mid-sentence. This practice gave his technical and physical mind a chance to rest before it got sloppy. More importantly, though, it kept his creative appetite whetted and active throughout the night so that in the morning he could pick up where he left off with renewed zeal. We can learn from Hemingway about leaving a little on the table when it comes to our pursuits.
It is often wise to quit while you are ahead. This strategy is called 'greasing the groove' in weight training and means that we practice strength exercises with the best technical accuracy possible, stopping before fatigue makes us fail or lose form. However, we must do the exercises more frequently. Over a period of months to years, the near-perfect practice results in longer-lasting strength gains than a traditional model that involves over-fatiguing the athlete. Applied to our day-to-day lives, this philosophy can be hugely effective. Consider the compounding effects of practicing a musical instrument or a foreign language for 30 minutes every day for the next year.
The Pomodoro Technique is a way to grease the groove at work. It involves eliminating all distractions for 25 minutes of intense work, taking a 5 minute break, and then repeating as necessary until the task is complete, or you run out of time. Usually 2 to 4 Pomodoros are enough to do a good chunk of work. The key here is 'undistracted working time,' a state of being that is ever rarer in our interconnected online world. Putting down your phone, shutting off your email/Facebook, and explaining to the people around you what you intend to do are all critical for success.
You don't need 25 minutes of time to grease the groove. Doing 5 pushups, 5 burpees, and 5 air squats every hour for a whole day will get you lots of reps. Or try to take 3 big breaths every even or odd hour. Or just take 30 seconds every morning before you rise to express gratitude for the good things and people in your life. The durations for these things can always be adjusted later. The consistent, focused practice is what counts. Good luck.