There are three broad groups of legally armed people. Each of them have different mandates on when and how they are to use their weapon.
A State with a capitol "S" is a general reference to government in general, and the national level of government in particular, like the State in George Orwell's nineteen eighty-four, not a particular state, like Ohio. The State has a monopoly for the use of force. The State can, has and will use violent force to further its’ goals, whatever those goals might be.
The Soldier is an instrument of the State to carry out diplomatic goals with other countries. Yes, warfare is the last step of diplomacy, which is all about a State getting other States to do what the first State wants the other States to do. In the words of Rush Limbaugh, “the purpose of the military is to kill people and break things.” So, their weapons are used in an offensive and defensive role as the situation dictates by their mission objectives. Their ROE (Rules of Engagement) span the spectrum from “You see, you kill” to “Do not engage unless engaged.”
The Officer is an agent of the State, charged with enforcing the laws on the books. The authority of that officer exists solely within their badge and position. The firearm(s) they carry are for defensive use only. If they made the decision to arrest you, the decision on if you’re arrested with extra holes in you or not is entirely up to you. There is a continuum of force hierarchy that agents must use during a police encounter. The only criteria they have in their shoot/no-shoot decision is if they feel they are threatened by you. And the State gives officers great latitude in that decision.
I illustrate this point using the Nashville School shooter. Due to the fact that she shooter was already shooting at police in the parking lot, I am 104% sure police lives were in danger. No opportunity presented itself to disarm and capture the shooter, so the police had to immediately go all the way up that continuum to lethal force.
The Citizen walks a knife edge. The State cannot Constitutionally restrict your Right to own, carry and use arms. What has happened is you have a legal minefield to traverse if you actually used your arms to defend yourself. You must prove to the prosecutor and/or the jury that all three legs of the AOJ Triad (Ability, Opportunity, Jeopardy) were active. You must prove your response was in the “Goldilocks” zone, not too much, etc. You must prove you tried to retreat, attempted to de-escalate the situation, and used every intermediate step of the Use of Force Continuum (or why you couldn’t) appropriate for civilian use before actually shooting your attacker. Your actions will be parsed to the millisecond and measured with a micrometer, then judged by a Monday Morning Quarterback to make sure you did everything right. And hang you buy your heels if you didn’t. Exactly zero latitude will be extended to you for having the unmitigated gall of protecting yourself and others.
Even if you pass all of those, you’ll still catch it for “discharging a firearm in city limits” or some such BS law.
In the end, don't try to compare yourself to an officer or soldier in the aspect of mandates or standards. You're all different in your capabilities, equipment, training, and purposes.