The Modah Ani is the first prayer that we say upon waking. (This could be said any time during the day when we decide to "wake up"!)
How often do we wake up without even thinking about the amazing fact that we are alive? Usually, the day will follow with a similar course of slumber. We never really woke up. We forgot that we are alive!
Each day is a miniature form of our entire of life. When we first wake up, we become conscience that we are alive. This moment is in a sense the beginning of our life. Our soul is now felt and we are refreshed. (Ok, so it may take a cup of coffee as well). The Modeh Ani assists us in experiencing this point in a complete way.