The older you get, the more fragile you understand life to be. I think that's good motivation for getting out of bed joyfully each day.
The winter solstice has always been special to me as a barren darkness that gives birth to a verdant future beyond imagination, a time of pain and withdrawal that produces something joyfully inconceivable, like a monarch butterfly masterfully extracting itself from the confines of its cocoon, bursting forth into unexpected glory.
If you can't do something willingly and joyfully, then don't do it.
I grew up hiking and horseback riding in Tennessee, so I love being outside. I will joyfully run 12 miles, but I'm not very good at boot camps. When they start yelling, I start laughing.
He who joyfully marches to music in rank and file has already earned my contempt. He has been given a large brain by mistake, since for him the spinal cord would suffice.