The past continuous, or the past progressive tense, allows us to stress that the action in the past had some duration.
A: What were you doing at 4 p.m. yesterday? B: I was playing tennis.
John was working all evening yesterday.
Past Continuous + Past Simple
The past continuous tense often goes together with the past simple. The past continuous shows a longer background action and the past simple shows the shorter action:
I was doing something when something happened.
I was having a shower when you rang the doorbell. was having — longer background action, rang — short action
Helen was cooking dinner when the children came back. was cooking — longer background action, came back — short action
It wasn't raining when I woke up. The sun was shining and the birds were singing. wasn't raining, was shining, were singing — longer background action, woke up — short action
Past continuous + always
You probably know that it is possible to use the present continuous together with the adverbs like "always" or "constantly" to talk about some repeated actions that we don't like. We may use the past continuous in the same way, but for the past.
He was always walking back and forth whistling loudly. That was very annoying.
Mr Sanders was constantly grumbling.