Staying positive is the only way to make this game work. When you are in a leadership role at a startup, you are responsible for driving a team with constant impossibility flowing around you.
At a talk he gave last night, Brad Feld, summarized this notion succinctly. To paraphrase, "every single day, there is something going on in my purview that is absolutely abysmal. Deriving energy and passion from it, and, more importantly, the overwhelming amount of positive events, people, projects that comprise the day, is the only way to make it work." It's a very "zen"-like perspective, and one I'm refining and fostering for myself.
If you need day-to-day balance in time, focus, and energy, startups likely aren't for you. You have to find consistency in chaos, clarity in mud, and calm in storms.