Write from facts rather than momentum
Pause long enough to remove accusations, assumptions, and details that belong to someone else. For a message about how to thank someone for a meaningful donation, use this factual base: name what the person did, when it mattered, and the practical or emotional difference it made.
Offer a proportionate next step
Match the size of the request to the relationship and to what the recipient can reasonably decide now. Thank them directly and share one honest outcome they helped make possible. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Protect privacy on both sides
Do not exaggerate, create a public spotlight without consent, or attach a new favor to the same message. Protect private health, financial, workplace, and family information when describing their help. Use the most private legitimate channel available and do not share the exchange to recruit support or pressure.