When I lift, I focus all my attention on the muscle being worked. Say for example bicep curls. I can curl a 50lbs dumbell for a good 8 reps, but if I really focus on the muscle and squeeze the muscle, I can only do about 25lbs for 8 reps. Should I be putting that much focus on the muscle? I get a great pump and I feel it a whole lot more but the weight I use is usually half of what I can lift normally. What's the best way to lift?