What is the moral or message of "The Nightmare Before Christmas"?

Summary

The Nightmare Before Christmas follows a very common trope called Home Sweet Home, but it does so in an unusual manner by making Jack initially bored with success, rather than having them be unsuccessful or an outcast.

Stories like these follow a general progression:

• The character longs for something else
• The character goes out to find that something
• The character realizes that they are happy back where they belong/come from

There are many varied stories about this, it's not always about personal philosophy as is the case for Jack. It can also be romantic (breaking up with someone only to fall in love with them again, which is what happens in Eternal Sunshine of the Spotless Mind). Or it can be about family (hating a family member, but eventually remembering your love for them, which happens to Alan Parrish and his father in Jumanji)

This same progression happens to Jack. In his quest to enrich his life (by taking on Christmas), he ends up relighting his original passion for Halloween.

Analysis

There are three songs that very specifically encapsulate these three steps: Jack's Lament, What's This? and Poor Jack.

The character longs for something else (Jack's Lament)

Yet year after year
It's the same routine
And I grow so weary of the sound of screams
And I Jack the Pumpkin King
Have grown so tired of the same old thing

Jack has grown indifferent to his success as the ruler of Halloween town.

There's something out there
Far from my home
A longing that I've ever known

Jack longs for something else but doesn't know what it is.

The fame and praise
Comes year after year
Does nothing for these empty tears

Jack is sad and nothing in his life is able to stop him from feeling sad.

The character goes out to find that something (What's This?)

Oh, I can't believe my eyes
And in my bones I feel the warmth
That's coming from inside

Could it be I got my wish?

Jack finds exactly what he thought was missing in his life.

I've never felt so good before
This empty place inside of me is filling up
I simply cannot get enough
I want it, oh, I want it
Oh, I want it for my own

Jack has fallen in love with the new thing (Christmas) and the rest of the movie (up until the climax) is Jack pursuing this new love of his.

The character realizes that they are happy back where they belong/come from (Poor Jack)

What have I done?
How could I be so blind?
All is lost, where was I?
Spoiled all, spoiled all
Everything's gone all wrong

Jack now realizes that his new love (Christmas) is just a folly, something that he wasn't able to fulfill.

And for the first time since I don't remember when
I felt just like my old bony self again...
And I, Jack, the Pumpkin King...
That's right, I am the Pumpkin King!

Jack remembers his identity as the Pumpkin King, the role he had come to loathe in the beginning of the movie.

And I just can't wait until next Halloween,
'Cause I've got some new ideas
that will really make them scream!

Jack's adventure has reinvigorated him and has made him appreciate the old love (Halloween) he had once become indifferent to.

What is the moral or message of "The Nightmare Before Christmas"?

The takeaway from this story depends on how you feel about it. There are different interpretations possible here, e.g. do you think Jack needed to pursue Christmas in order to re-find his love for Halloween? Would he have not found it again if he had stayed in Halloween town? Do you think Jack's takeover of Christmas was ill intentioned or well intentioned?

It's hard to answer what the morale here is without knowing your interpretation of whether some of Jack's decisions in the movie were right or wrong.

However, I do want to add something that was never added in the movie, the real closure. This is official canon, but it was only added to the soundtrack, not the movie itself. I find this a missed opportunity because it very much shows an integral part of Jack's character after the events of the movie:

I asked old Jack, "Do you remember the night
When the sky was so dark and the moon shone so bright?
When a million small children pretending to sleep
Nearly didn't have Christmas at all, so to speak?

And would, if you could, turn that mighty clock back
To that long, fateful night, now, think carefully, Jack
Would you do the whole thing all over again
Knowing what you know now, knowing what you knew then?"

And he smiled, like the old Pumpkin King that I knew
Then turned and asked softly to me, "Wouldn't you?"

Jack is back to his old mischievous self again. Not only is he back to being himself, but he also no longer regrets taking over Christmas (which he initially does in Poor Jack); which suggests that Jack now considers these events an integral part of who he now is.

Jack followed his heart, and it happened to lead him back home. Regardless of whether it brought him home or not, following your heart leads to happiness.

And that, in my opinion, is the real morale.

My interpretation:

There are plenty of "explanations" but my opinion after watching The Nightmare Before Christmas was, that the beginning and the end of the movie tells the story;

Jack misses something even though he is the "king" of the town. The solution was not having something new, different or more. The solution was that he ignored Sally the whole time and she was the missing part of his life.

Also: it is not important what or when you celebrate, it is important with whom you celebrate and you don't ignore them the whole year! And remember them only in holidays.