I should have known better.

Meaning

Expressing regret for a lack of foresight.

Examples

• John: 'That was a foolish mistake.'
• Alice: '<b>I should have known better</b> than to trust them.'
• John: 'Yes, <b>I should have known better</b> than to invest in such an unstable market.'
• Alice: 'I really regret that investment.'