To complete a task efficiently with high quality results I’ve found that slowing myself down and concentrating on it to then execute it purposefully is faster in the end than rushing through it just to complete it quickest. When I don’t slow myself down, I find that I’m not satisfied with the quality of execution and the final result and have to do it all over again. Or I make mistakes and have accidents that require more work to clean up. All result in slower execution than doing it slightly slower in first place. So I tell myself: “Slow down to speed up”. But this works only if you’ve already mastered the skill of fast execution. Procrastination shouldn’t be slowed down ;-).  You should always challenge yourself to complete a task in an aggressive time frame with the risk of not achieving it. That way you discover optimizations unknown to you before.