Prompt: the nicest thing someone ever said to me
Response: It feels odd to share with others the nicest thing someone ever said to me because it seems private, and also like boasting. Why? Because the three things that come to mind were all affirmations of me as a person, or the person I would like to be.
But a fourth thing comes to mind, also very helpful--that I will share. Once when I was in existential free-fall, someone told me--if not precisely in these words--"It will be all right." Now, that's a ready-made phrase. But it became powerful to me later when, finding myself (as I often do) facing someone else's crisis, thinking back on the exchange someone had with me and saying "It will be all right."
Now, I don't know how much good it did the person, but I know it did NOT hurt him/her, which was gracious, because my usual response at that time would have been irritation and probably cross words. "It will be all right" was the perfect phrase, and one of the nicest phrases someone told me, because it made me nicer.