My favourite part is the experimentation and adaptation. When I started on YouTube I was completely clueless, and navigating pretty much blind. Even with all the great resources out there, channels like VideoCreators etc, my implementation of the strategies I learned from those channels was.. to put it bluntly, pretty awful. Over time I've experimented with different strategies, trying out different titles, different description styles, different thumbnails styles, different ways of marketing products etc.
I'm still very much figuring things out but I've learned so much in my time on YouTube, and it's an exciting process as you start to figure things out and get an intuitive feel for how certain things work. Perhaps the most exciting part is whenever a new idea comes into my head for something completely different to try - those first few days when I'm trying it out, and eagerly checking my analytics on a regular basis to see if it's working out.. They're exhilarating!