Decelerating during chipping causes golfers several problems and makes it very difficult to achieve a good connection with the golf ball. If you are decelerating as you play your chip, the club head will be slowing down as it approaches the ball.
This will make it very difficult for the club head to move through the ball and will lead you to hit the ground before you strike the ball. The result will be that the chip doesn’t move forward very well and it will end up short of the target, sometimes only moving forward by a few feet. So decelerating will cause you to hit the ground before the ball and also cause you to hit shots that fall short of the target.
If you find that you are struggling with your chipping, look at where the club head is finishing once you have hit the shot. If you are decelerating during the chipping action, you will notice that the club head stops as you attempt to swing through the ball or that it finishes only a foot or so after the ball.
In order to improve this and to start to accelerate the club head through the chip, initially work on achieving a swing that has an equal backswing to follow through. For longer chips, you will be swinging the club head back to about waist high on your backswing, so work on swinging the club head through the ball so that it finishes at waist height. Your swing should always be equal in length on both your backswing and follow through. However far the club head moves to the right of the ball, it should mirror this movement and move to the same distance to the left of the ball on your follow through. Work on swinging waist high to waist high and this will encourage you to maintain the speed in the club head throughout the shot.
Another drill you could work on to maintain the speed in your club head on long shots would be to work on your timing. As you swing the club head away from the ball, count to yourself - 1, 2. Count 1 as you start your backswing and 2 as you reach waist height with the club head. Now swing down and count 3 as you strike the ball and 4 as your reach waist height on your follow through. Work on keeping the speed that you are counting constant and getting the club head into the correct position on the correct number. Maintain a constant speed, counting 1, 2, 3, 4, with 1 starting the backswing, 2 being when the club head reaches waist height, 3 being impact with the golf ball and 4 as you follow through and reach waist height.
This will also get you accelerating with the club head when playing chip shots and with the club head now accelerating you will find that you start to strike the ball much crisper and find that the golf ball now reaches it's target rather than falling short.