Compare the past continuous (I was doing) and past simple (I did):
Past continuous (in the middle of an action)
Past simple (complete action)
- I was walking home when I met Helen. (= in the middle of walking home)
- I walked home after the party yesterday afternoon. (= all the way, completely)
- Sarah and Carol were watching television when the phone rang.
- Sharon watched television a lot when she was ill last year.
We often use the past simple and the past continuous together to say that something happened in the middle of something else:
- Tony burnt his hand when he was cooking the dinner.
- I saw you in the park yesterday. You were sitting on the grass and reading a book.
- While I was working in the garden, I hurt my back.
But we use the past simple to say that one thing happened after another:
- I was walking along the road when I saw Lisa. So I stopped and we had a chat.
- When Jason arrived, we were having dinner. (= We had already started dinner before Jason arrived.)
- When Jason arrived, we had dinner. (= First Jason arrived and then we had dinner.)
There are some verbs (for example, know/want/believe) that are not normally used in the continuous:
- We were good friends. We knew each other well. (not “we were knowing”)
- I was enjoying the party but Mary wanted to go home. (not “was wanting”)