I would think it would be the same as any mentally challenging activity. Similar to studying or chess or whatever…anytime your brain is working full time but the body is not. The solutions I have used (for studying) is to take breaks when you feel the motivation slipping. 10/15 mins is often enough. Make sure you maintain adequate food intake for energy. When you do eat, make sure you get some food with instant energy like fruit (straight fructose/glucose conversion). Adequate sleep the night before also plays a vital role.