Just like consciously choosing your mood, you can choose to feed your mind uplifting material before it has a chance to absorb anything negative. Keep a stack of inspirational or motivational books by your bedside. First thing in the morning pick one up and open to a page randomly. Read the passage your eyes fall upon first, and take a few moments to reflect on how it pertains to your life.
You may also post inspirational quotes on your fridge or mirror.