What you should have practiced as a quick reaction is just instinctual. Maybe you've just done it that many times or you just help allies without a second thought? Or maybe? Just hear me out on this one... You practiced more.

1st Style: When a creature you can see attacks a target other than you that is within 5 feet of you, you can impose disadvantage on the attack roll. This can now be executed up to a number of times equal to your proficiency score times without a reaction. The usage resets at the start of your turn. You must be wielding a shield.

2nd Style: When you or another creature within 5 feet of you make a dexterity saving throw, you can use your reaction to give advantage to yourself and that creature for that saving throw. You must be wielding a shield.