Lol! I have learned the same with my 12 week pup! We also had trainer come to the house about a week ago for a "puppy manners" class! He was exactly what I needed. Some tips the trainer gave us that may help others too:
He said excessive biting is 1) a toy problem 2) a treat problem. 3) overtired puppy
1) I thought we had enough toys but in reality our sweet boy was already tired of his toys. He was going around those boring toys and biting my arm. We got a few more toys and have been rotating them every day or so. It's like a brand new toy when we pull it back out after he he not seen it for a day or two! He gets so excited seeing the new toy, he forgets about my hands. The other key to this is to have 2 toys going at once! When he is overly excited and comes back at me to chew me, I whip out the other one! Oh happy dog!
2) treat problem...he was tired of the same ole treats. At the suggestion of the trainer, I purchased one of the cold rolls of Nature's Pet food rolls for puppies (around $5). I cut it up into pieces for a training session. He loves it and his little brain is so tired, he usually goes back to sweet puppy after one of those little snacks and training sessions (and learns my hands produce yummies!) I am sure there are lots of other delicious things too like chicken, ground turkey, etc
He also suggested ice cubes and frozen carrots to entertain him when I just can't. This morning he wanted to play, but this mama needed to unload the dishwasher! He went through two ice cubes and I got my job done.
And finally, he goes nuts in the mornings when our 2 children (ages 7 and 10) come downstairs biting their legs etc. so I started putting 2 toys and some treats on the stairs before they get up so they are "armed and ready" to interact with him for a few minutes. I also have been making them keep treats nearby at all times so as soon as he comes for them, they can start doing some commands/treats which usually satisfies the dog and keeps the from bleeding! Lol
Hopefully we are in the home stretch of the land shark phase and you are too!