Guys! I have a good

Guys! I have a good question!

If I already have a chord progression and I write a melody on top of it, how do I know it’s the right melody for the song?
How do I know, from the very first step, that I’m building something I won’t regret later or feel is “unstable”?

What’s your trick for making sure the whole production stays in the sound-world you want? (Like staying close to your reference.)

And how do you personally know when each element—sound selection, chords, melody, rhyme—is the right choice?
Like…How do you know?