别放在心上。

You usually say this after someone apologizes to you. It works as a stand-alone sentence. You can also add 没关系 (it's okay) before it. It sounds very natural and kind. It is like a verbal pat on the back. Use it to dismiss a small debt or a minor accident.

Use it when a friend spills a little water on your table. Use it when a colleague misses a non-urgent deadline. It is perfect for texting a friend who is over-apologizing. In a restaurant, use it if a waiter is too sorry for a small delay. It makes you look like a relaxed, generous person. It creates a friendly atmosphere instantly.

Do not use this for massive life mistakes. If someone crashes your car, this might sound too dismissive. Avoid using it if you are actually very angry. It is for small social frictions, not deep betrayals. Also, do not use it with your boss if they are scolding you. In that case, just listen and apologize!

Chinese culture values 'Mianzi' or face. When someone makes a mistake, they lose a bit of face. By saying 别放在心上, you are giving them their face back. You are saying the relationship is more important than the error. It reflects the value of harmony in social circles. It is a way to maintain 'Renqing' (social favor) without keeping score.

You might hear 别往心里去. This is almost identical but feels a bit more northern. You can also say 没事，别放在心上. Adding 没事 (it's nothing) makes it even more casual. If you want to be very short, just say 别介意. But 别放在心上 is the most poetic and warm version.