Narnia Prince Caspian

Best spot to grab this achievement is on the Miraz's Castle Assault, theres a whole bunch of barrels and crates lieing around as well as a couple blue shards, after you have destroyed everything possible and grabbed every possible, enter a mission which should save it, then quit that mission and you will reload at the same spot with every thing there again.
To get max health you have to have your health bar full of blue, it should go brownish, gold, and then finally blue.