What can you absolutely, positively, not get the hang of...no matter how hard you try?
I can't ride a bike. I didn't need it when I was younger (everything was walking distance). Tried when I got older, and I just couldn't get it.
I also have no sense of direction. It takes forever for me to figure out how to get somewhere. It's a running joke with all of my friends and family. I can do anything with numbers that you need, but I can't tell you, turn by turn, how to get to my house from work.