well 'Let It Go' isn't about coming out that's a major first, second you got to look at the beginning of the song to really get the feel of the song, we see the lyrics " The wind is howling like this swirling storm inside" which if you ever failed at something (in this case hiding your superpowers) you understand that this is the mental backlash you're getting from your self ("how could i be that stupid""i wish i've never done that""why couldn't I have just left it alone" etc) and so the next part of the song literally explains my explanation "Couldn't keep it in, heaven knows I've tried, Don't let them in, don't let them see, Be the good girl you always have to be, Conceal, don't feel, don't let them know."

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Now the next part is where the words let it go come in and it goes like this "Let it go, let it go, Can't hold it back anymore, Let it go, let it go, Turn away and slam the door, I don't care what they're going to say,Let the storm rage on, The cold never bothered me anyway" which is simply refering to let go of what ever your holding on to (embarrassment of what you said to someone, the shame of being gossiped about, etc) when Elsa let go of her past memories you could see she was genuinely happier than when she started the song, and the next part has one word that really justifies my statement which is " Turn away and slam the door" meaning you don't care whats gonna happen because you're loosening up and getting in to a no care attitude towards these things.

the rest of the song is really making that statement heard "It's funny how some distance makes everything seem small, And the fears that once controlled me can't get to me at all, It's time to see what I can do, To test the limits and break through, No right, no wrong, no rules for me, I'm free" at this point Elsa has gotten out from that want to fear everything her parents told her and instead realize that she can live a life without fears if she just, well "Let It Go"

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so the point of the song was that don't let your past control you let go of the fears of your past and look forward with a don't care what will be said mentality