The mind muscle connection makes all of the difference when it comes to stimulating growth and detailing quality muscle. If you are not squeezing and contracting the muscle each rep of each set then you are
selling yourself short. It will not respond to it's full potential. You need to be able to feel the muscle your are working do the work not all of your secondary muscles taking on a unnecessary workload. I believe in stimulating and not annihilating the muscle. This means training hard but training smart. In my opinion you should not pay attention to numbers and how much you can lift because honestly nobody really cares. And if
you care then you're ego lifting. Training too heavy will only increase your risk of injury and chance of sacrificing proper form. That's just going to slow progress and that's not what we are trying to do. Mind muscle connection is not something you can easily learn overnight and it takes years to master. I've been training now for about 7 years and each year the connection is still improving.