My second rule for being ultra-productive is to always stay indoors and make a special effort to stay up very late to wreck your circadian rhythm.
This will serve the dual purpose of depriving you of vitamin D and fresh air and staying up late will ensure you feel horrible for hours after waking up because your body will never properly adjust to going to sleep and waking up at different hours every day.
So do not go out and stay up very late every day.