Your reply makes me think of CT's I, BOdybuilder.
Always lift the weight as hard and as explosive as possible. In other words, each rep, regardless of the weight, should actually be a maximum effort. Acceleration is very important, as well. Try as hard as you can to make sure you actually accelerate the weight on every rep.
Hard. Explosive. Accelerate. Every rep. It's the only way to produce the maximum force possible.
Quality of rep performance, on every single rep, should be your only concern.
This means that for most of your training, you won't be lifting above 85 percent of your 1RM. In fact, the usual training range is somewhere between 50 - 85 percent of 1RM. Just remember, every single rep of every set is performed using maximum force.
Don't worry about training with weights that you might perceive as "lighter" (below 80 percent 1RM). This system will soon enough have you toying with your current personal bests."
But instead of using 3 reps, you'd use more reps which apparently will over tax your CNS.