on a good note 尽欢而散；欢尽而散

【例句】
After the party, we said good-bye on a good note.
晚会后我们尽欢而散。

The reason for the split has not yet been confirmed but it has been reported that the two bid each farewell on a good note.
分手的原因还没有得到证实，但据报道两人是尽欢而散。