Hindsight is 20/20.

Meaning

It's easy to see mistakes after they've happened.

Examples

• John: I should have studied harder for that exam.
• Alice: Yes, but <b>hindsight is 20/20</b>. What's done is done.
• John: I know, I just feel really frustrated.
• Alice: We all make mistakes. Just learn from this one, and remember <b>hindsight is 20/20</b> next time.