1. It's harder to focus.
When you're younger, you're so horny you can't think. When you're older, you think too much. I'll be ready to start and suddenly think: I've got to pay the electric bill. We only have a quarter of a roll of toilet paper. Why didn't I pick up toilet paper? She told me to get toilet paper. Is this going to be a thing now, that I forgot the toilet paper? Fucking toilet paper! Did I lock the door? I thought I locked the door. Should I get up and check? I don't want anyone walking in and seeing the weird shit I'm watching. I'm kind of hungry. Maybe I should just forget it and put on True Detective instead.
2. Death of imagination.
The only fantasy I have room for in my life now is Game of Thrones, or that my vote will make a difference. Most of my dreams have died or been gradually compromised and I'm not about to muster the effort to visualize something naughty with the taut tattooed girl from the gym obsessed with squatting. Way too much work. I'm more likely to take a Pilates class. I've also been with my wife for over 14 years and my Personal Masturbatory Rolodex became obsolete when Al Gore invented the Internet. The only memories I have left of other women are so old, it would be like trying to whack it to faded ghosts and white noise (sad, confusing and a little creepy). Pornography is the simplest solution.