A little story: I was climbing an elm over a roof once, and it was real hot. 7/8ths of the tree was on the ground. The heat didn't bother me, I was used to it. Then I started getting weak, and I didn't feel right; kinda dizzy! I thought to myself, "I can finish this tree, then I'll relax. Just a few more cuts..."
And shortly thereafter, I badly misjudged a cut, and ripped the service line off their house. Then I spent the next 45 minutes on my back, drinking water and trying to recover from some heat exhaustion. It was 100% climber error: I was hurrying to get down, and I did it wrong as well. All the warning signs were there, I just wasn't paying attention. I had a tree to finish!
If your back is talking to you, you probably need to pay more attention to what it is telling you. Just sayin'.