当写感谢信的开头时，可以使用以下万能句："Dear [Recipient's Name],I am writing to express my heartfelt gratitude for [specific reason for writing the letter]. Your [action or gift] has had a profound impact on me and has left me feeling incredibly grateful. "当写感谢信的结尾时，可以使用以下万能句："Once again, I would like to express my sincerest gratitude for [specific reason for writing the letter]. Your kindness and generosity will always be remembered and appreciated by me.Thank you for being a part of my life and for making it more meaningful. I look forward to our future interactions and the opportunity to return your kindness in the future.Warm regards,[Your Name]"这些万能句可以根据具体的情况进行适当修改和调整，以确保感谢信表达出真挚的感激之情。

无论是开头还是结尾，都要确保表达出对收信人的尊重和感激之情，并表达对未来关系的期待。