Hypothesis: when you speak [1] you often subconsciously generate sentences with nice prosody. I think you may also do this when you write - but only on the first draft when you're streaming your consciousness.

The reason I say this is that when I go back and edit something I've written, I may end up with something that is factually and grammatically better, but I often find myself stuttering ("in my head") as I read it because I keep trying to put weight in the wrong place. It's like I've broken the prosody by changing words out of order.

(It could also be something weaker, like I simply remember the intonation from when I first wrote it rather than there being anything "right" or "wrong".)

[1] English has its own rules about the timing of syllables that are different to other languages. Eg. what I say here probably doesn't apply directly to Italian.