I recently saw a presentation by Neil Pasricha on TED TV. After some heavy dissapointments in private live, he decided that he two choices. Let life bug you and be sad all day, or enjoy life and take every moment to make a happy day.
He started a blog called 1000 awesome things, in which everday he describes an awesome thing that you can find in very small and simple things in life. Think of having the perfect ketchup on your fries.
I think the same goes for innovative people. You will per definition be bogged down by people that tell you that it will not work, that you will not get the money, that the market is not ready for it and that is has been tried 1000 times already.
Every time you have this feeling, just visit the 1000 awesome things website and realise that you can find your own awesome moment that will give you the required energy again.