I wouldn't bother too much. This may affect you into thinking you lost 10% of your time, but you don't. If you try to be 100% all the time, you'll end up with a

I wouldn't bother too much. This may affect you into thinking you lost 10% of your time, but you don't. If you try to be 100% all the time, you'll end up with a burnout. Appreciate this time, do some reading, finish loose ends. Focus on quality, not on quantity. Tell your boss that this is you. You need that time to recover, so you can focus on the new project. It's like with sporting - a professional sporter plans his recovery time. What you do is professional sport as well. Take care of yourself. It's long term vision.