^^^ definitely look at what @PamPurrs has said.
Also I’ve found that I went through the death grip phase,still occasionally do but it does get better the more you play.
I’ve also found if I’m playing something more difficult it happens more. It’s really a case of remembering to breathe as Josh days in the B2B and trying to relax/enjoy yourself
Well… yes and no. I practice sitting down, resting the bass on my leg. The strap is fairly slack in this position, so if I let go with both hands, then the neck drops more than I would want it to. But resting my right hand on the body is usually enough to hold it in position, so I don’t think I’m holding it up (too much) with my left hand.
Has your bass been properly set up? Sorry if you covered that before. But it should take very little pressure to properly fret a note.
It’s correct that the pressure fretting is countered by the hand/forearm on the body of the bass, when fretting with no thumb. But it should not be overly difficult.
Also the goal of this exercise is not to fret that way all the time, just to accustom you to how little pressure it actually takes. Do this for a few minutes and then practice/play as normal, using your thumb.
Agreed and good point, @howard and @akos . . . if the action is too high, it’ll definitely take a toll on the fretting hand and musculature.
No setup, I’m playing it as it was shipped from the factory. I’ve been planning to look into the setup for a while now, but I’m concerned that I’d just make it worse. (I know I’m supposed to take it to a professional, but I’m way too lazy.)
Yep I know, it just felt really awkward and inefficient, and wanted to make sure that I’m not spending my time practicing something silly here
Doing a setup is really not very hard. Marcelo’s how-to video gets posted a lot, but here it is again 
Seriously it will take like 10 minutes
I find it is totally like golf. When I relax and breathe during the swing, I am okay. Then when I tense up and try too hard…trash! Since starting the course, I am beginning to understand subtlety. Slowly.
I did this too, wound up hurting my hand. Don’t play if you’re injured. But for me and many others a lot of these bad habits dissappear over time.
I think I’ve accidentally improved my death grip a lot this month.
I spent the past two weeks in DGCF tuning (learning Nirvana songs), and due to the reduced string tension, I was able to play with less pressure on the frets. My fingers got used to the lighter fretting, and it seems to have carried over when I returned to EADG this week: I’m still only applying the DGCF amount of pressure, and everything still sounds fine.