The Passage of Time
You reach a point in your life when the saying "there are more days behind me than in front of me" really means that. Time and biology combine to work their inevitable alchemy on your body, leaving you with thinning hair, an expanding waistline, increasing wrinkles, and wattles of flesh about the neck. Even the mind begins to loose it's capabilities; facts are lost, and the limber mental gymnastics you used to perform in pursuit of the furtherance of your carrier grow ever more difficult.
As a Christian my faith is supposed to be strong enough not to let the thought of death bother me. But my faith, like the rest of me, is imperfect at best, and like my flesh grows more feeble as time passes. The root of my faith isn't in me so much as in my lovely wife, the woman who's health disability has caused her far more physical suffering than I've ever experienced. The woman with three back operations, who had to have her left knee replaced twice because the first operation left a colony of MRSA that eventually grew and put her in the hospital with a constant temperature of 103. A woman who suffered from this and far more. In spite of all of that her faith is still strong, far stronger than mine.
The 28th of October is her birthday, the start of a four day celebration that ends on Halloween. I won't say how old she is, out of decades of growing respect and love. I hope she's with me for a lot more birthdays. For on the day she passes on, she'll more than likely take me with her.