Math
I have a complicated relationship with math. I really hated it in school. But somehow I found out that I liked studying it on my own. I taught myself first semester calculus well enough to test out of it both at U of Iowa and at Indiana. I did get through a second semester calculus course at Indiana but it was painful because of my trouble understanding infinite series. Looking back I really should have made more effort to ask for help by going to office hours and stuff. At one time I had collected a large library of math and physics books but self study didn't get me much farther.
I still have my calculus textbook from IU and would like to master vector calculus but it unclear if I have much actual motivation to do it at this point in my life.
I do have some sincere interest in learning topology. A number of years ago I bought some cheap Dover textbooks and I was looking at these recently and felt some interest in really trying to jump into this. I have some experience with mathematical logic having taken a course at IU and the beginnings of the topology textbooks don't look too difficult. It is just a question of forming a determined mind to do it.