Keeping your left elbow straight is a myth in the golf swing; people who are built thick through the upper body can’t keep their elbow straight without picking up on the backswing
The most common fault in pitching is taking the club too far back and decelerating on the downswing, practicing how to finish your pitch will solve this problem
Play the ball forward, use more arms and hands and try former U.S. Amateur Champion Hank Kuehne's trick for selecting the right club