Handwraps, properly applied, are necessary. Second, a good pair of bag gloves is essential. It's the wrong glove for the bag. Hitting the solidly packed bag accelerates the breakdown of a boxing glove. Hitting the bag with improperly wrapped hands or no gloves accelerates the breakdown of your hand.
Proper form means hitting the bag flush with the fist for a safe and efficient workout.
The hardest thing to unlearn in boxing is a bad habit. The easiest way to avoid this is not to get the bad habit in the first place. Practice your combinations slowly to master the technique and then ramp up your speed. Placement is essential. Hit in the center of the bag.