Own it to the pager. A service isn't done when it's merged. It's done when I'd be comfortable being the one paged for it, and I usually am.
Design for the failure, not the demo. Every external dependency will rate-limit, time out, or lie eventually. The architecture decides whether that's a log line or an outage.
Measure before and after. 18% to 5%. 5% to 1%. 10x. If I can't put a number on the change, I'm not sure I made one.
Use AI, review everything. I use AI coding tools every day for boilerplate, tests and debugging. I don't let them make design decisions, and nothing they write reaches production unread.