on approach speed is controled by the elevator.....so you're giving an up in put which slows the plane and you stall on to the deck....altitude is controlled by throttle....next time try and add a couple of clicks of throttle and take those clicks right back off again..watch how the descent rate slows and makes a slammer landing into a smooth one...once again its throttle up and then throttle right back to idle.....you don't have to hold the power on....
next time you're on approach...don't make any other corrections except throttle add say 1/2 throttle and watch the plane climb......then set up again if your sink rate gets to be to much add power not elevator....Good Luck