We use Past Simple with actions that started and stopped in the past, i.e. they were completed:
I broke my leg
This is the main difference between Past Simple and any tense from Continuous Line of Past Tenses
She was doing her lessons (It’s not stated if she completed her lessons or not)
She did her lessons (it’s clear now that she finished doing her lessons)
They were going to the movies when we met them yesterday (it’s not stated if they finally went to the movies)
They went to the movies yesterday (we know that they completed this action)
You don’t really have to read the following unless you want to:
Some teachers explain other tenses like Present Perfect from the point of view of representing the fact of an action. I avoid this terminology as Past Simple, in the example above, shows the fact of going to the cinema as well. Though, explaining Present Perfect from this point of view has some grounds if explaining like so: Present Perfect is used to show the fact that something has happened and Past Simple is used to show when or how something happened. For the purpose of this lesson, let’s just skip this controversial discussions here.
Action in the negative form
Action in the negative form becomes inaction. If we use the negative form of this tense, it is still a completed inaction.
They did not go to the movies.
In a nutshell:
We use Past Simple when actions were complete, actions that started and stopped in the past, in the negative constructions, we can revert this as: inaction was complete. Simply saying, an action started and stopped or did not start at all.
Also on Past Simple: