To echo that, your teacher should be saying "Do this" instead of "Don't do this" when it comes to
anything.
As someone who had this same issue, here's what I'd advise for next steps (until a better teacher can be found to help refine it).
- Learn basic scales, Major and Minor ones. This is insanely basic to do and that's why I'm suggesting it first. Here's why:
- All you need to focus on to improve this is the concept known as "economy of motion". Don't use more movement/space/energy than you need to get the job done. There's two things to practice that should dramatically help with this.
1) Plan out your hand position. A good rule of thumb (and it seems your fingers are long enough to do this effectively) is to do "1 finger to 1 fret" for the scale you are doing. With Major scales, you should be starting with your
middle finger for the root note and on Minor scales you'll start with your
index finger on the root note. When you look at the shape of the major
scale on a fretboard, it will make a lot more sense. Basic Minor Scale shape is
here. Different scales have different shapes, once you learn them you shouldn't have to think too hard about which finger to play the root with.
2) Keep the pad of your thumb pressing against the back of the neck, essentially parallel to it (but make sure the position is decently comfortable to you). Don't press too hard, but you should be able to make a decent pinch without cramping. If not, try loosening up a little and adjust the height of your thumb in relation to the neck. After a while, this will come naturally to you.
- The next part is only achievable with practice...keep your finger pads hovering above, but not touching the strings when they're struck. There's really no way around this, you just need to practice it with intent. This is a lot easier when you aren't having to radically change your hand position (see the part about scales and the "1 finger to 1 fret" method). Once you're nailing this with ease on basic scale shapes, then I'd move on to more complex fretting techniques and movement.
Then it's just down to finger strength (from practice) and muscle memory. Chromatic runs are good for warmups, just start REALLY slow and focus on technique. We're talking half notes at 120bpm or slower to start off. I also warm up by skipping a fret (as in doing Index Finger -> Ring Finger -> Pinky) on the next run and alternating that around. The idea being that you're getting comfortable with whatever movement you'll have to do when fretting. When you've gotten better, you can move onto string skipping, octaves, walking basslines, etc. A good teacher should guide you through this appropriately.
Hope this long-winded post helps! I not only had more stamina, but my playing and timing cleaned up considerably after doing this. Welcome aboard and keep pluckin! (or picking...or slapping. W/e you like best

)
EDIT: In all that advice, I neglected a very important point lol. Make sure when you're fretting a note, you are doing it JUST behind the fret itself. This will minimize fret buzz and while a pain at first, will help in the longrun. Also, I'd check out Scott's Bass Lessons on Youtube. Guy has some excellent content, but I'd just focus on that stuff first as things can get pretty complicated rather quick with online instruction. He has to keep making content to get views and revenue, so there may be a lot to sift through with a lack of clarity on where you should be or progressing to.