yuē hǎo yīqǐ chīfàn, kāihuì huò bāngmáng, rúguǒ línshí lái bù liǎo, yào jǐnzǎo shuō

约好一起吃饭、开会或帮忙，如果临时来不了，要尽早说。

If you've agreed to eat, meet, or help out together but can't make it, let others know as early as possible.