To be truly happy, you need a clear sense of direction. You need a commitment to something bigger and more important than yourself. You need to feel that your life stands for something, that you are somehow making a valuable contribution to your world.
Here's a philosophical rule of thumb: always start with the negative definitions. Negative definitions are always easier to understand. So, here's a negative definition. We must not conceive difference in terms of the differences we find between things that already exist. Difference is not empirical differences.