Subjunctive Mood: If I were ...
Even though the past tense of "to be" usually requires the form WAS for the first and third person singular (I/he/she/it), there is one exception which needs to be taken into account.
For hypothetical situations the SUBJUNCTIVE MOOD is used.
Here are some example sentences:
Most commonly, this construction is used, if you imagine yourself in the position of another person and wish to give advice.
If I were you, I would not send this letter.
If I were you, I would be more careful.
If I were you, I would ask her out for dinner.
Furthermore, if you express a wish that is unlikely to happen or a situation that is impossible, WERE is used instead of WAS.
If I were rich, I would travel around the world.
If I were a dog, I would lie in the sun all day long.
If I were a film star, I would not give any interviews.