“They said that Dioscorus of Namisias made his bread out of barley, and his soup out of lentils. Every year he made one particular resolution: either not to meet anyone for a year, or not to speak, or not taste cooked food, or not to eat any fruit, or not to eat vegetables. This was his system in everything. He made himself master of one thing, and then started on another, and so on each year.” (The Desert Fathers: Sayings of the Early Christian Monks)
Very good advice on productivity from a most unexpected source! Master one thing at a time. Don’t move on to the next thing until you’ve mastered that one thing. Also, learn something new every year.