Past Conditional sentence

A past conditional sentence describe what is that was not true or didn't happen in the past, these sentence contain a clause beginning with if ... (states the imaginative condition) , and a main clause (explain the result of that condition).

If I had stayed, I would have gone crazy.

Past conditional sentences have an unusual verb structure:

Conditional clause Main clause

If + past perfect + (should/would/could/might) + have + past participle

Some Examples:

If I had owned a car, I would have driven to work.
If i had seen her, I would have told Mary.