As I approach age 50 this year, I am learning to appreciate youth again, if only because now it is a distant fantasy rather than an identity I can cling to. My teen daughter and youthful girlfriend seem to be egging me into decrepitude, forever underscoring all of the vital functions (hearing, seeing, memory, walking, etc.) I "really should have checked." "Did you just wheeze, Dad?" asks my daughter -- followed by Nurse Girlfriend checking my pulse. Is it any wonder I find the childish enthusiasm surrounding mobile so invigorating and addictive?