When will you know it's time to hang up your whistle?

[Love2ref4Ever]

Officiating is a love of mine, and being the best that I can be at this advocation is very important to me.I have been thinking about how will I know it's time to stop officiating.When this day comes I hope it will be a act of my own free will,instead of some assigners telling me that they can't put me on certain games anymore because I can't get up and down the floor.When this time comes how will I know it's time to hang up my whistle?