goatigirl,
You can also have a chair right behind you, so when you get to that "enough" point, you can smoothly and effortlessly sit down and continue your exercises without missing much of a beat. After spinning the energy ball in your lower Dantain as Z mentioned, you can do the full Harvesting of Qi (if you have the time - it's good stuff), or an abbreviated version like Master Lin guides you through at the end of the Small Universe meditation.
Much Love,
Shawn
