I've always thought that life goes through times you feel like you're on a mountaintop, and times you feel like you're in a valley. The valleys are definitely not fun, but I always know that they can't last forever, and soon there will be another mountain to climb.
It's a pretty basic life philosophy that keeps me encouraged when I'm feeling low. But lately I've discovered there are more geographical features than just mountains and valleys. There are also plateaus.