Recognize what makes this moment difficult
Acknowledge the event directly without turning it into a lesson, comparison, prediction, or silver lining. For a message about how to apologize for revealing a friend's private struggle, use this factual base: identify the moment, the impact on trust or inclusion, and what your friend should not have had to carry.
Offer support that can be accepted
Offer one specific form of practical or emotional support and make clear that no immediate reply is needed. Offer a repair that matches the harm and show how your behavior will be different. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Follow their pace rather than yours
Do not use shared history, mutual friends, or public gestures to pressure a private response. If contact is unwelcome, stop and avoid using mutual friends as messengers. The recipient decides whether they want conversation, ordinary company, practical help, professional support, or quiet.