The item in mind is the Enchanted Jewelry which can prevent one stamina damage any phase (and gets discarded once 3 stamina tokens have piled up on the card). Does this mean it can only be used to prevent 1 stamina loss during that phase, or can I prevent 3 damage at once?
The only reason that you would be unable to repeat the "Any Phase" ability on a card is if you must exhaust the card to use the ability (e.g. Dragon's Eye), or if it explicitly says that you can only use the ability once per turn (e.g. Mandy Thompson's ability). Since the Enchanted Jewelry meets neither of these conditions, it can be used multiple times per turn, including repeatedly from the same attack. The same also applies to the Shotgun.