I wrote a Blender plugin that uses vector math, matrices, calculus, trigonometry, and likely other types of math. There's recursion, filesystem access, image processing, interface logic, and on and on.

And worst of all - other people are expected to use it, so there's added pressure to do a good job.

Oh, the hours I spent trying to figure out why the imported geometry looked like an exploded mess. Fumbling around with mathematics I didn't fully understand was exhausting. Finding help was impossible at times because I didn't have the vocabulary to even describe the problems I was having. And getting it to complete an import before the heat death of the universe was not easy.

Every time I made progress and thought I was done, I would discover a bug that other importers didn't have, leaving me to sift through languages that definitely aren't Python to see if I could reverse engineer the logic they used.

I almost gave up a few times, but didn't.

Now I have something that, while not used by many people, works very well, is very efficient, and doubles as a palette cleanser when I need to do something for fun or for a challenge. Plus I learned a lot along the way.