Work out what you're actually asking for, ask for the conversation properly, open in words you'd really use — and know what to do when it gets hard, including stopping.
A request, a grievance, and a hope they'll reassure you — bundled together. None of them gets addressed, and both of you come out feeling it went nowhere.
Delivering prepared paragraphs at someone who's replying means half your attention is on getting back to your place. The useful part of a hard conversation is usually the part you didn't plan.
No subject, maximum dread, and they arrive braced to defend. A short message naming the topic lets someone turn up able to think about it.
Once either of you is too worked up to think clearly, continuing is how the thing gets said that takes a year to undo. Twenty minutes apart, with a stated time to return, isn't a failed conversation.