10 rounds of Dominion later I finally read the rulebook
I played Dominion with my group for about 6 months before someone pointed out that buying multiple copies of the same action card lets you play each one, not just one. I thought it was a bug in the rules, so I checked the manual at a game night in Austin, and sure enough, I had been nerfing every deck we built. My friend laughed and said it explained why my win rate was stuck at 2 out of 12 games. Has anyone else had a rule you missed for way too long that changed everything once you caught it?