I am an ASE Master tech and have been since the mid 80's. I also have the ASE engine performance certification. I was in the automotive industry for about 28 years, working on vehicles, shop foreman, and eventually parts and service director for a dual line dealership. I have maintained my ASE certifications even though I no longer work in the industry. I love puzzles and logical thinking, which serves me well for diagnosing vehicles.
I would train new technician trainees when they were hired. I found that I really enjoyed seeing them "get it" when I was teaching them something new. I still enjoy teaching.