Make the first sentence usable
Lead with the reason for writing so the recipient does not have to decode a long emotional introduction. For a message about how to apologize for smoking around someone, use this factual base: name the missed care, privacy breach, exposure, comment, or accommodation and its practical effect.
Reduce the work of responding
Offer simple options, a narrow question, or a clear update that can be understood without another conversation. Correct what is still correctable and ask what support is useful rather than prescribing it. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Respect the boundary already visible
Do not debate symptoms, disclose medical details, or make the person reassure you. For urgent symptoms, exposure risk, medication errors, or safeguarding concerns, contact the appropriate clinician or emergency service. A block, explicit refusal, legal restriction, or safety plan takes priority over the desire to explain more.