Hey everyone! I've been looking for a subreddit to ask this question and hopefully this is the place.

So recently I have finished a project that took me a little more than 20 days, which was a small C library with 43 small functions that "copied" original ones like strlcat, strlcpy, memcmp and such. When I went to hand in the project yesterday, I realized in shock that I had no clue of how my code worked anymore. Surely enough I could remember what each function was about, but just by looking at it for a fee seconds wasn't enough to make my own logic clear to myself; I'm not talking about a lot either, just around 30 lines of code per function or something.

So my question is: Is this kinda stuff normal or am I failing at some point? Are there strategies I can take to improve this and actually remember what I wrote?