It's hard to put it into words and I would describe it more as feeling like being one with the force.
There is a reason why this scene is so iconic and moving.
I would say it is essence of good versus evil, having a pure heart and doing the right thing no matter the cost. There isn't a sufficient adjective to describe this but this is why Rose is just an absolute outrage and Episode VIII needs to be removed from the timeline. You can describe the Rebel Alliance as the principled and determined good guys with an establish and shared ideology and set of goals. There is no way in a million years a rebel would do what Rose did.
Films like Star Wars teach you that (and I could say Gladiator, The Last Samurai, Hunger Games, Babylon 5). You may argue things aren't as black and white as that in real life but it is a good starting point. Start off with good standards, morals and principles and go from there.
In a way you can hold the Jedi up to be the gold standard in terms of ideals, keepers of the peace and discipline. Although it isn't and shouldn't be all about them, due to the position and power they hold within the universe their attitudes and behaviours influence and rub off on other people (e.g. Obi-wan to Luke to Han). You have a person or people setting an example of what it is to be a perfect person (subjective), this is how we lead our lives and always try to do the right thing and you can choose to follow our example or ignore us. That is in the story and it is fiction but as we all know, characters in films and tv series, good or bad, influence us. There are numerous examples in the news of people over the years who have been influenced by evil characters in films and committed murders etc. The Fast & Furious films are always funny when they get released for the fandom and racing it inspires but why not hold Star Wars up as the shining example of what it means to be the best person you can be with regards to purity of spirit.
As another example if you want to step away from Star Wars, lets look at the MCU and Avengers. Everyone has their favourite. Mine is Captain America. Regardless of story, film or scene, you watch it and think "if that situation arises I would like to think I could do that or behave like that". You are given a baseline to model yourself on of values and behaviour and you tweak it from there. I think Star Wars is a perfect example of that and the reason why it is so special is because other than something like B5, it has the benefit of time (duration) to impart that philosophy and ideology on multiple levels in multiple examples from multiple characters.
So go to back to your question and getting to the point, I would define a true fan as somebody who appreciates the essence of the mindset I have described above and sees Star Wars as more of the sum of its parts. It isn't just another random scifi fantasy action film. There is an underlying message and rich story it is trying to convey. The first six films were very consistent and did this perfectly imho but the new trilogy failed spectacularly; it was all style and no substance. They tried to be Star Wars and there were moments, but only got 40% of the way there.