Don't be afraid to throw something out you don't really need. Have a yard sale or liquidate through eBay. If no one buys it, it's time to give it away or throw it out.
Note that this doesn't work on really stripped screws. Simply cover the screw with the flat part of the rubber band. Unscrew like you would normally, but add a bit more pressure than you're used to.
Getting organized with your important documents makes things less stressful the next time you begin digging through random boxes searching for your social security card (if in the US), birth certificates, car insurance information, or even your passport.
If you keep forgetting that you closed the garage door, when it closes, say out loud: "The garage door is closed". Or when you wonder whether or not you unplugged the iron. "The iron is unplugged". Your brain will become more stimulated to help build a stronger memory.
"Work hard, play hard" is probably the most mainstream version of this ideology, but it's absolutely true, in order to be a top performer at anything. The most productive people regularly take a step away to process what you are doing and plan out where you are going. It also helps avoid burnout.
Staring directly at your destination instead of other people in the eye will signal to them to get out of the way.
Measure your hand from your fingertips to palm and memorize it. Now you can judge the size of anything without a ruler. Try to pick a finger that's pretty close to standard length (~1 inch).
You'll never forget it. Place it inside your shoe if necessary.
No time is better than the present to make changes. Stop thinking in the past and continually look forward to the future.
Shoes, tires, beds, office chairs, couches, etc. You will thank your future self for doing so.