Debugging
There's a certain joy derived when tracing a problem to its root. Say you're writing a program and it mysteriously starts failing. Debugging such issues can be almost exhilarating with a mixture of frustration. Most times, I imagine this is the feeling that hunters get when they are trailing game. Tongues out, almost panting, eyes furrowed in concentration, trying a different things, learning, repeating with minor variations and checking the results. I have delved in node modules, composer's vendor files while debugging and its probably the best way to get good at programming.