I’ve come to a new obvious realisation with this sort of thing recently: if you care about some metric, make a test for it early and run it often.

If you care about correctness, grow unit tests and run them at least every commit.

If you care about performance, write a benchmark and run it often. You’ll start noticing what makes performance improve and regress, which over time improves your instincts. And you’ll start finding it upsetting when a small change drops performance by a few percent.

If you care about memory usage, do the same thing. Make a standard test suite and measure it regularly. Ideally write the test as early as possible in the development process. Doing things in a sloppy way will start feeling upsetting when it makes the metric get worse.

I find when I have a clear metric, it always feels great when I can make the numbers improve. And that in turn makes it really effortless bring my attention to performance work.