Change the shield protection

With a shield, explosions, like TNT, creppers, beds (in the nether), whiter explosions, etc, should protect you between 50-60%, when a mob attacks you, like a zombie or enderman, the shield should protect you between 75-80% (depending on the damage caused by the mob), and also, if a stalactite falls on you, the shield should protect you completely (if you are protecting yourself by looking at the scalactite), although it would hurt the durability of the shield a lot, even if you have Unbreakability III.

Other damage, such as arrows, would protect you 100% of the damage and the cooldown caused by the axe would be maintained.