I just started working out a week ago, but I've realized that my performance drops off between sets. What I mean is that say I'm doing incline bench press, 70lbs.. the first set I can do 12+ reps. But on the 2nd set I fail at 7. The third I fail at ~5, sometimes as low as 3. I am resting between the sets. Should I use less weight initially, or reduce weight for each set? I want to do around 8 reps failure. Is this problem normal?