A few months after retiring I decided to pursue music as an activity. I spent some time on the internet and bought a few books on bass playing. But it quickly dawned on me that I would do better taking private lessons.
When I started looking for a teacher I wanted to find one who was also a performer. I really lucked out with my choice and I’m still studying with him today. He has a large number of students, plays in multiple orchestras (on upright bass) as well as in jazz and metal groups (on electric). (I frequently joke that he’s the hardest working man in show business…)
A few years later I decided I also wanted to play a chordal instrument (you can play chords on the bass but I was thinking piano or guitar) so I started guitar lessons but I have those lessons half as frequently as my weekly bass lessons. That too has proven to be a good idea.
Aside from the educational benefits, lessons for a non-performing aspiring musician like me serve the purpose of accountability. Not that I don’t come to lessons unprepared at times but when I do it’s a non-musical lesson that reminds me I have to get back on track.
YMMV but for me lessons are one of the main reasons for progress in my musical journey.