The description of the Boon Life Affirmation reads: "Any (Heart) chamber rewards are worth more." But there's no type of chamber that just rewards you with a heal. There's the centaur hearts that give you max health, the treasure troves sometimes have healing in them, you can buy healing from the Well of Charon and then there's the food that drops sometimes. So which of these does Life Affirmation affect? And are there any others I've missed?
If you look closer, you'll notice that there are 2 types of heart icons: one with plus and a regular one.
The heart with a plus means healing, the heart without a plus is increase of health pool + healing. Life Affirmation Boon gives you bigger addition for your health pool for Centaur Hearts and rewards for Chaos Boons that increase your health pool. I don't think it works on Cerberus' trinket that increases your health pool though.