Here's how my boxing lessons going :
First few days : the full cotton filled punching bag felt like a stone bag. And skin over my fist got broken in two or three days. Was punching only Jabs then. Nothing more. And not more than 3 at a time. Got tierd everytime after delivering only 3 jabs. Forget delivering 6.
Now : skin over fingers regrew. And the new skin doesn't feel as much hurtful as before. Plus don't get tired after delivering 3.
Can deliver about 30 punches at a row shaking the bag.