I used to teach prosody. I am plenty mean. I write bad poetry. I love good poetry.
As for line breaks, and punctuation, they're like everything else in poetry: every technical decision justifies itself by delivering meaning. This goes for free verse as much as for non-metrical verse. Free verse just doesn't have meter and rhyme in the mix. In all poetry, you're looking for the maximum consonance between meaning and form. That's the real trick.
And free verse does have some conventions concerning line breaks. Heavily enjambed lines, which run sense and syntax over the line endings into the next line, are associated with content that is meditative, private, deeply thoughtful. This is the kind of line Starbeam suggests. Lines, especially relatively long lines, that allow a complete through to end with the end of the line tend to come across as public, certain, or oracular. And Berrylovely strikes a middle ground in "Lonely Moment." I'd say Berrylovely's choice is fine for her content. She's talking about a limited time: one moment. And she describes separate thoughts and feelings within the moment, each moment-within-the-moment gets encapsulated in its own line, it's own tick or tock of the duration of the moment.
Example of heavily enjambed:
THIS IS JUST TO SAY
I have eaten
the plums
that were in
the icebox
and which
you were probably
saving
for breakfast
Forgive me
the were delicious
so sweet
and so cold
--William Carlos Williams
For the oracular, public kind of verse, take a look at Walt Whitman.
There are other ways, of course, to structure lines, but I've been boring long enough.
