Put it up next to the piece of paper with your mission written on it, so in the morning and after lunch, when you are reviewing your emails, you feel empowered to ignore most of them, answer only those that are most important or urgent to you, and to respond with a (more polite) no to those making demands on your time and energy that do not service your mission. No, I’m not interested. No, I can’t attend. No, I’m not available. No, I won’t do that. The more you say no via email, the more effective you will be.