To maintain the handle in front of the clubface at impact, you need to develop a flat left wrist (right wrist if you are left handed).
What happens with most club golfers, is that they allow the right wrist to straighten. This collapses the left wrist, resulting in a loss to the width of your swing arc, which causes those topped, thin and hitting the ground behind the ball shots.
Look out for this the next time you play.
Fellow of the Professional Golfers' Association