Right arm resting on the body of the bass - Check.
Nice comfortable wide strap - Check.
Not having to “push” with my left thumb whilst fretting - OH CRAP. LoL
I knew I was hurting for some reason!
Thanks @JT!!
PS - Love Ariane. Pretty technical on most of the stuff I have watched of hers, but I enjoyed it. And, I have her iTunes version of “Cello Suite #1 in G Major, by Bach” played on an Electric Bass as my arm clock each morning. 
I was similar. Not pushing hard with my thumb, but found it hard to play while not using my thumb at all. Been trying to get better at that and slowly improving.
Yep practicing for a few minutes at the start of every session without using your left hand thumb at all is very helpful.
I had no idea until playing after watching this that my thumb is doing so much pushing!
One more thing to work on…its a journey for sure!
The infamous death grip is certainly part of the journey and will pass pretty quickly if you watch what you’re doing.
I certainly went through it , asked the knowledgeable community here and got over it eventually. And just to give you some idea how bad it was I struggled to slide my thumb up the back of the neck when I was playing 
If your hand/arm starts to hurt. Stop. For a bit. Let yourself recover. Increments. Breathe like Josh says you should… I swear he is talking to just me exactly when I am holding my breath :). But seriously don’t ignore pain. It’s there for a reason. I overdid it practicing and now I wear a copper fit brace like Brett Favre…not happy.
+1.
Definitely do not try and tough it out through injuries. Pain is there for a reason.
This is great! I might have to work on a “Left-Hand Anatomy” video to go with my “Slap Anatomy” so I can visualize how NOT to f*ck up my left thumb (any more than it already is). 
If you do work on a video for this, maybe call it a “Fretting Hand Anatomy?”
IMHO, as a lefty, it does cause a millisecond or two of confusion, even annoyance, whenever anyone (not picking on you @kristine) refers to the hands as “left” and “right” (when speaking of playing bass and/or guitar), as it is the opposite for approximately 10% of us. To me, it seems more inclusive to refer to the hands as either the “fretting” or “plucking or picking.”
And yeah, we do figure it out, so take my opinion with a grain of salt. 
Just sayin’!
An excellent and appropriate suggestion, @Never2Late ! I am also a lefty (but I play right-handed), so I probably should have thought of that. 