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 only asking a friend for favors, use this factual base: identify the moment, the impact on trust or inclusion, and what your friend should not have had to carry.
Reduce the work of responding
Offer simple options, a narrow question, or a clear update that can be understood without another conversation. 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.
Respect the boundary already visible
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. A block, explicit refusal, legal restriction, or safety plan takes priority over the desire to explain more.