Today I'm the happiest I've ever been.

[lagoo]

Today I'm the happiest I've ever been.

from: https://www.healthymummy.com/the-happiest-ever-been/
And some similar sentences are like:
I'm the healthiest I've ever been!
I went from a major health scare to the healthiest I've ever been.

My question is:
Shouldn't there be a "than" to make the sentence grammatical, which should have been "Today I'm the happiest than I've ever been"?

 

[Tdol]

No- you could say that you are happier than you've ever been, but there's no need for than with a superlative.

 

[lagoo]

We use 'than' with comparatives, not with superlatives.

Goodness me. I made the most basic grammatical mistake.
Actually what I wanted to say was this sentence seemed to have missed something.
I'd like to come up with some more basic superlative sentences to draw a comparison to the one in my original post.
1. I'm the happiest in my class.
2. I'm the smartest of all the students attending this test.
3. Today I'm the happiest of all the time I've ever been.
4. Today I'm the happiest I've ever been. (the one in my original post）
So, you see, unlike the other three, there's not a single preposition in #4. So to me, it's like an ungrammatical sentence. How does "I'm the happiest" connect "I've ever been"?

 

[GoesStation]

1. I'm the happiest in my class.:tick:
2. I'm the smartest of all the students attending this test.:tick: [except for the underlined word. You don't attend a test.]
3. Today I'm the happiest of all the time I've ever been.:cross:
4. Today I'm the happiest I've ever been.:tick: (the one in my original post）

The word "that" is optional after "happiest" in number 4.

 

[jutfrank]

I went from a major health scare to the healthiest I've ever been.

I understand why the grammar of this sentence may seem odd to you but it really is very natural to use a clause after a superlative to make a noun phrase. Here are some more examples:

That was the longest I'd ever spent abroad.
The closest he came was third place.
This is the most you'll ever earn.
Is that the best you can do?

In each case, you could use that after the superlative to connect the two parts, but in casual speech we often don't.