Past perfect tip:
This verb tense is often used to express a cause and effect relationship in the past, made explicit by including the keyword because.
I went back home because I had forgotten my wallet.
My smartphone service stopped because I hadn’t paid the bill.
Another past perfect tip: it’s very good to use past perfect with when in a sentence involving two actions as it clarifies the chronology.
Compare the difference:
When I arrived at the club, the band had already started playing.
When I arrived at the club, the band started playing.
