That was a mistake.

Meaning

Acknowledging an error in judgment.

Examples

• John: <b>That was a mistake</b>. I should have listened to your advice.
• Alice: It's okay, we all make mistakes sometimes.
• John: I learned a valuable lesson, though.
• Alice: Glad to hear that! I really think next time, you won’t make a mistake like that again. But honestly, <b>that was a mistake</b>.