Check your ego at the door and grow! Your muscles can't tell how much weight you are holding in your arms and you shouldn't care also. Heavy weights only fuel the mind and often the mind lives in a different place than reality. Have you ever questioned someone like Kai Green doing dumbbell curls with 35 pound weights or Shawn Rhoden squatting 225? Whats up with that, are these guys lazy or are they smart!? In reality they are utilizing something called time under tension and they are taking the muscle as close to failure as possible. They will hit out 15-20-25 reps with perfect form and concentrate on the squeeze with each rep. The amount of time it takes to complete such a high number of reps is where the stimulation and muscle growth will come from during the lifts. They are also activating a number of different types of muscle fibres that will grow bigger during recovery. It you take this simple tip and put it into motion you'll see better results quicker.