For me, it was realizing that I wasn't any better or worse than the other people on the team, and that my opinion was just as valuable when discounted by my exp

For me, it was realizing that I wasn't any better or worse than the other people on the team, and that my opinion was just as valuable when discounted by my experience level. Before that, I was always reluctant to speak up, or express any strong opinions, because I was always surrounded by people who appeared to have their shit together and were very confident and forceful about expressing their opinions. I've probably overcompensated since, but finally allowing myself to feel that freedom to just say, "No, I think that's not the right way, we should try this instead," has allowed me to progress much farther than any technical achievement I could name.