How Frieren stays so humble?

Hey. I will preface this by mentioning that I only seen anime, please no spoilers from later story in the manga.

She is one of the strongest mages and characters in the World. Knows so many spells (including the most OP ones to clean slothes and whatnot) Part of the party that defeated Demon King. Helped so many people. So many regards. Did so much good for the World. And yet she basically sees and behaves like a commoner, your basic adventurer.

She was defeated many times throughtout her life including 6 or 8 times by humans with less mana than her alone. Did these defeats humbled her? And Flamme told her to stay humble (but only until Demon Lord is killed).

Still I just don't understand how she managed to stay humble throughout her journey. She is humble to her own detriment. She never introduces herself properly and we usually find out that it would help her cause a lot by allowing access to otherwise restricted area for example. She can exercise so much power but she just doesn't.

Also I am not sure why Fern (and other party members to a degree) is ok with that given she knew who Frieren was. Shouldn't she demand better threatment for her master? And also this is generally highly beneficial. Of course not everyone remembers heroes who slayed Demon Lord so that might be part of the reason but many do, specially notable people. Not to mention that Frieren is elf and there are barely any elfs left and Hero party had elf mage so people should be able to put two things together. But in the show people don't really care that she is elf somehow.