Something I wish I understood earlier about holding index ETFs

When I first started investing, I spent a lot of time trying to find the right strategy. Over time, I realized that simply holding broad index ETFs like QQQ, VOO, and SPY taught me more than most of the things I was trying to study. Not because they are special, but because they expose you to your own behavior. There were plenty of days where I felt the urge to sell everything, especially during drawdowns. There were also periods where I wanted to add aggressively after strong runs. I started keeping notes on those moments. Nothing complicated, just what I felt and what the market was doing at the time. Looking back, most of those decisions would have been driven by emotion, not by any real edge. It took me a while to accept that managing your own reactions is a big part of this. Probably more important than people want to admit. Took me longer than I expected to figure that out. Curious if others had a similar experience