Theology is one of those funny things. There is nothing more important at all than Theology, but at the same time it really doesn’t matter. At the end you either love God or you don’t and no amount of theology can change that. Maybe it changes how you love God, good theology lets you love God more fully - but it doesn’t save you.
Once saved always saved is the only bone I have to pick with the protestant church. Most protestant churches have the sense to moderate this somewhat. They sell it as a 100% absolute, but then chip away at the doctrine around the edges inferring things like, “look at the life so and so is living, they were never really saved!!”
Lutherans however double down on this particular doctrine. It is really more akin to saved against your will and held hostage. I had a Lutheran pastor actually explain salvation and grace as force feeding. It makes no logical sense how they talk about it and they can never give you a clear definition only that Jesus does everything for you and you do absolutely nothing.
Here is why that is bad. If you have no agency and are compelled to heaven, then there is no reason to be mindful of how you live and what you do.
We shouldn’t live in fear of hell every time we cuss someone out for cutting us off in traffic or see an inappropriate image, but we should care about these things. If you are cussing all of the time, that should worry you as a Christian. We are trying to be like Jesus, not sort of kind of like Jesus. We are to be an imitation of him as one would see in a mirror, lot like something that was ordered off of wish.com.
It’s not ALL taken care of for you magically and the spiritual life is not automatic save for those rare moments when God gives you grace to overcome certain sins.
Don’t live in fear of Hell. You MUST live in fear of not loving God as much as you could have during your brief time on earth. Once saved always saved can get in the way of that.