つい〜てしまう

N3

ついV（テ形） + しまう

「つい〜てしまう」表示不经意间或情不自禁地做了某个动作，常常带有后悔或意外的意味。
可以理解为“不由自主地做了某事”，有时带有一种无法控制的意味。
比如，你本来不想吃零食的，但一不小心就吃了，就可以用这个语法来表达。
总之，是表示做某事是无法避免或无法控制的情况。

The grammar pattern "つい〜てしまう" is used to express an action that was done unintentionally or accidentally.
It often conveys a sense of regret or surprise that the action happened.
For example, if someone says "つい忘れてしまった" (tsui wasurete shimatta), it means "I ended up forgetting (it)" or "I accidentally forgot (it)", indicating that the forgetting was not intentional.
This pattern is commonly used to describe actions that happen spontaneously or without much thought.

してはいけないと思っていることを無意識にしてしまう。 後悔の意味。