You reflect and think your life over -- if it's been good, bad, or if you fill fulfilled or not -- and start the changes from there (for the better, of course!).
This could have other definitions but mine is that you delve into your heart and see how it compares to God's desires for you. What you want and what He does. It also means that you start asking...
I beleive that the soul is like another part of us humans, if we didn't have a soul we would be like a light bulb with no electricty, a spacesuit with no astronaught.