Our apartment is old, and we have a set of 3 keys needed to access our apartment. To make matters worse, they all looked the same! I was thus forever using the wrong one and swearing at the doors.
Then, I had a fabulous idea to end all of my troubles.
I simply painted the tops of each key with a different color nail polish. One of my keys did already have a color key on it, but I painted it gold anyway so it wouldn't be left out...
I can't tell you how much difference tiny change has made my life!