The first instruction in the entire Jewish law code (Shulchan Aruch) is "Be strong like the lion when you rise in the morning to serve your Creator.""
Each night, as you fall asleep, your soul ascends to heaven to recharge. In the morning, waking up signifies that God has returned your soul to your body, giving you the gift of life. This, in turn, means there is a part of this dark world you must illuminate. God trusts you to accomplish this task.
That is why the first phrase one says in the morning is: I thank You, living and eternal King, because You gave me back my soul with grace, great is Your trust.
This is the thought that runs through your head when you get up and start the day.