Start with the part that is verifiable
Separate the event you can describe from the motive or reaction you are guessing. For a message about how to tell your spouse you want a separation, use this factual base: name the current pattern, concrete impact, and decision that needs both partners' attention.
Make one answerable request
Give the recipient one concrete question or next step instead of several emotional jobs at once. Ask for a time and format to discuss one issue, then identify any outside support that could help. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Leave the recipient in control
Do not threaten abandonment, use intimacy as leverage, or demand an answer during an unsafe or heated moment. Use specialist domestic abuse or emergency support when coercion, violence, stalking, or immediate danger is present. A clear message remains useful even when the answer is no or no answer arrives.