All day you’ve been thinking about this blog post and what you will write. It’s your birthday, and it’s tradition that you write something snarky about aging. Some people will tell you they love growing older–maturing, growing up, watching their kids grow, maybe even becoming grandparents. It’s a lovely thought—growing old(er) naturally—as if we actually have a say in holding on to youth and beating Father Time. We don’t. Aging is not fun. So your birthday looms. It’s the big 5-0. You think about it for weeks. It practically consumes you. You notice every grey hair, ever extra mile you have to walk to shed .001 pounds, and each line…