You already have a plan in place here, so my intent isn’t to talk you out of that, but I completely get this, and something I’m a fan of doing is approaching squats with a built in fatiguer ahead of it so I can tell myself that THAT is why the loads are so light. It’s absolutely disheartening when you set yourself up for optimal performance and then can’t move the weight you want to move, but if you set yourself up so that you’re coming into the final sets fatigued, it’s far easier to swallow.