You know, what really surprised me was how natural it came. I'm not saying I didn't make mistakes, or that everything worked the way I thought it would. It's that whether I had a plan for a session, was winging it, or was crafting long term setups that didn't pay off for months, it flowed for me.
Reading my players, adjusting to the vibe of the table, switching things on the fly, it wasn't a struggle.
Mind you, that's my first campaign. There was a little bit of struggle learning d&d as a whole, and that learning curve meant the previous adventures were clunky as fuck all because I was just wrong about a bunch of stuff. Thac0 alone was a huge factor. But once I grasped the rule set, making my own campaign and running it felt as natural as breathing.