​past simple vs past continuous

​We use the Past Simple for:

1) a single completed action in the past

2) a repeated action or habit in the past

3) a state in the past

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​We use the Past Continuous for:

1) an action in progress at a point of time in the past

2) the background events of a story

3) an action in progress when another (shorter) action happened

​used to

​We can use used to when

1) it’s a repeated action or a habit in the past

2) it’s a state in the past

​3) it talks only about the past

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But we can’t use used to when

1) the sentence talks about one action in the past