Hiring managers, big companies, and schools aside, how do you tell for yourself if you yourself are a good engineer or not? For all the metrics such as load tim

Hiring managers, big companies, and schools aside, how do you tell for yourself if you yourself are a good engineer or not? For all the metrics such as load times, conversion rates, income, bounces, etc. to measure our machines, what metrics do we have to measure our professional selves for our own personal growth? Is it how many side-projects I've shipped? How many users / downloads I have? How well I can grok complex systems? How well I can solve specific and difficult programming challenges? How many javascript frameworks I can code HelloWorld in? If we had a choice (we don't), how do we decide if we should invest in ourselves or not?