my problem was that i got used to the bag too much. i got used to hitting something all the time, and when i shadowboxed, i was just off, i would just screw up, i couldn't get any combos going well, and it took time to fix. basically, focus on speed and combos, and try not to have the mentality of putting everything into a punch, focus on fluid combos. work on your technique. speedboxing can be a learning experience. besides, when people train on a bag, they are just looking to beat it up, which may result in repeated uppercuts and just trying to maul the thing, not thinking "if this was an assailant, i would be hit".

make sure you are able to keep punching fluidly, not letting yourself get off balance, which means doing the right combos, and not letting yoursel open. for the "not letting yourself get off balance", here's an example: right hooking, then right uppercutting. a simple example of flaw. make sure you can continue to punch safely and effectively.