Show your teacher this:
Then walk out and get another teacher.
This is text book (below) and doesn't work for a lot of people. It doesn't work for me at all.
It is contrary to Adam Neeley's video above.
Watch videos of your fav bass players and most of them don't play the way shown below either.
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Also, you'll have bass teachers who are guitar players who want you to keep your fretting fingers perpendicular to your fretboard while teachers who are actually bass players want you to keep your fingers as parallel (flat) against the fretboard as possible as another way of muting when needed.
Teachers should inspire, not 'rip you a new one'.
Granted, they're not there to tell you you're great when you're not, but there are better ways to get you to change bad habits and work on time.
I've been taking lessons for about 5 years. I am currently taking a break from lessons as I am working on finger picking. I am a pick player and just felt I needed to do this on my own and then pick my lessons back up when I feel more comfortable playing with fingers, but that was my choice and not my teachers. I still suck and am on my 4th teacher, but I am not ever giving up. My current teacher makes his living from 100% music.
Also, if you've been playing for 40 years why exactly are you taking lessons?
G.A.S. happens from seeing something that you really like or are really curious about. All I can say is don't look and you won't get G.A.S. as much.