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. There is a reason that old bags are taped around their midsections. Over its life, that's where most of the punches landed. As you started to work the bag, you moved in and out. You snapped a perfect jab, but there was no bag to meet your fist.