What makes you cringe looking back at your beginner self?

I think I was a bit of a smartypants in the sense that I didn't realise people had written sub-optimal code because of pressure by time or from management or a similar aggregator. So instead of just tactfully proposing an improvement, I think I represented it more like "By the way guys, it's much better to do it like this!" 😬 (because I genuinely thought they didn't know of approach X).

Someone should've smacked me or set me straight, but they were very kind and forgiving about my newbie-enthusiasm.