not for an instant

例句：

1. 1. I'll never forget the day wemet.
   我永远不会忘记我们相遇的那一天。
2. 2.He promised to come back tomorrow, buthe didn't.
   他承诺明天回来，但他没有。
3. 3. She said she would helpme, but she didn't.
   她说她会帮我，但她没有。