A few things I've learned over the last year that I was supposed to learn when I was 5
Tying my shoes
I learned this one last year actually, and the previous year has been SO MUCH BETTER because of it.. Basically, until last year, I didn't know how to properly tie my shoes... and odds are, you might not either.
I always thought it was because my shoelaces sucked or something, and I always found myself double knotting. Turns out, I was just tying the knot wrong. There's an easy way to test if you tie your laces wrong.. just shake your shoe a little, and see if the bow orients vertically instead of horizontally across the shoe. If so, you're doing it wrong. To fix it, just reverse the first knot (for example, if you normally go left over right, go right over left instead). It looks like there's already a web page, with pictures, describing this whole thing.. who knew?
All my life, people have remarked that I have well developed calves.. I thought maybe it was just genetic, but I noticed neither of my parents had them. Over the past year, I've lived on a hill where I basically have to climb up about 200 stairs to get home. Today as I was walking home, I somehow noticed that how I climb has changed to a much more efficient method. It turns out that I USED to put my foot only halfway onto the next step, then used my calf muscles to lift my body. Now I (like normal people) lift my knees just a wee bit higher, enough to get my entire foot planted squarely on the next step, and then use my quadriceps (the muscle on the front of your leg, above the knee) to lift my body. Of course this is easier because quads are a lot stronger than calf muscles, since we use them a lot more. I don't think this problem is as common because most people's calves aren't super huge.
Now I have the choice of either climbing the stairs easier, or maintaining my calf definition. At the very least, this explains why I was pretty good in high school at the long jump and triple jump, and why I could touch rim when I was only 5'6"
I hope I just made someone else's life a little bit better. Especially on the shoe tying one. Honest. It'll change your life.