We use the past perfect to show that an action had already happened before another action in the past. For the main action we use the simple past. For the earlier action we use the past perfect.
When the kids got up, their parents had already had breakfast.
Nobody had helped me, so I couldn’t finish the job in time.
He looked a lot better after he had lost some weight.
We cannot use the past perfect without thinking of another action or time reference in the past:
He didn’t see the end of the movie because he had fallen asleep.
To talk about several actions that followed one another we use the simple past.
He stood up, walked to the door, slowly opened it and found a dog sitting outside.
Think of two things that you did yesterday. Say what you did in one sentence using the past perfect with a time word for the earlier action. Practice this tense contrast with similar action pairs.