When you try to defy your age by challenging your 7 year old nephew to a game of golf on the XBox360, even if you kick his butt, you will still prove you're too old to play when you have to put on your glasses to read the information on the screen about your golf statistics (and even then you can't read it all).
When you take your niece shopping for new school clothes, after handing her no less than thirty pairs of jeans of various sizes and styles, you will find yourself cursing the sizing discrepancies from brand to brand and complaining about how they ride too low, or are way too long, or there is just no reason for a 12 year old's jeans to cost $40, only to find yourself sounding exactly.like.your.parents 25 years ago.
If you tag along for school supply shopping and find yourself explaining with passion to this same niece that it is the FOLDERS that are the most exciting part of new school supplies and choosing them is an activity that should not be taken lightly. When you find your voice getting slightly too animated, with a bit too much enthusiasm as you explain the lengthy process you used to go through each and every year of carefully selecting your new supplies and agonizing over just exactly how you wanted to organize yourself for classes, she will, in fact, roll her eyes and give you that look that reminds you she doesn't believe folders were even invented when you went to school.
While waiting on your lunch order at the Food Court, you actually take notice that every.single.person behind the counter was probably born after you graduated from high school. Not only that, but they all have two things you would never have dreamed of in high school, namely, either a) a visible piercing in a location other than their ears or b) hair color that is far from natural.
You actually catch yourself saying, "just because all your friends have cell phones doesn't mean you need one."
When you make an attempt to recreate a lesson plan you taught during your student teaching days and realize that in order to find the resources you need, you're using a technological advancement (the internet) that wasn't available when you taught the lesson in the first place.
Realizing for the first time that your sister has wrinkles under her eyes (sorry, Jules) and looking in the mirror and realizing you do, too.
When you've watched 400 of the 500 laps of the NASCAR race at Bristol only to go to bed before the finish because it's 11:00 and you have church in the morning.