The best way to tell if you're old is to fall down in front of a crowd of people.
If they look at you at laugh, you're still young.
If they run to you in a panic, then you know you're old.

That sounds reasonable.

Yesterday, I went to the park with my wife, son, and four grandkids. I was watching the kids play. There was a device on the equipment that was something you hang on to and ride for about 12 feet. My son said I should do it. You may recall that I had shoulder surgery back in December. I was feeling pretty good. I reached up and grabbed it with both hands. When I put my full weight on it (215 pounds or 15.4 stone), my shoulder made itself known. Woah! I don't know if I will ever get it back fully, but I hope so. I guess 6-8 months recovery may be the case. I am only about half way through that. I guess I will never play football or pitch again. HA! I am old.

Silly me. I thought the best way to know if I'm old is to look in the mirror.

No mirror required for me. My joints keep reminding me.

I have a sleep number bed. In years past, I would spring out of bed, refreshed and ready to go.

Now, no matter the sleep number I choose, it hurts to sleep more than 5 or 6 hours.

When I was younger, I could sleep for 12 hours or more and not feel achy when I got out of bed.

Also, if I don't shave every day; my white whiskers remind me that I am just rotting fruit on a vine.

Well, at least you haven't lost your positive outlook.

During the course of my recent flubug, I didn't shave on Saturday morning(when I was feeling my weakest). I FELT old because I couldn't manage shaving, and I LOOKED old by seeing what was quickly growing. But in spirit I'm still young.

My 3 week old beard is much grayer all over than it was a few years ago, the last time I had one.

I feel old. Worn out.

Yes when i miss a few days my white facial hair reminds me that im not young anymore lol also glad im not alone in this . Thank god the hair on my head hasnt changed to white yett.

At 47 I am still not that old. What makes me feel older is telling all the kids the things 'OLD' guys use to tell me. I guess it's just being a grumpy old guy.

I got one when todays music bothers you and you start talking bout back in my day thats when you know you turned into your dad aka you are old hahaha

Bonus points if you start wearing your pants up around your armpits.

with socks and sandles

Physically old, yes.

...or your bra around your waist.

Another indicator is when they start calling you sir.

Not for me.
We had new Air Force recruits coming in calling me sir when I only had three stripes!