1. It's not a good idea. You eat too little.
If I were you, I would eat more.
2. I love animals. I want to become a vet.
If I loved animals, I would become a vet.
3. The post office worker lost this letter.
If I were the post office worker, I wouldn't lose this letter.
4. Jane didn't want to go to the theme park. She stayed at home.
If I was Jane, I wouldn't stay at home.
5. You will have a wedding next week. You must be happy.
If I were you, I would be happy.
