Question: Is there a difference when the adverbs '*always, continually,forever,etc..*' are used with past simple and past progressive?

For example :

1. He **always/ continually** worked there.
2. He was **always/ continually** working there.

(What is the difference between the above two sentences?)

Answer: 
Let's say that a colleague mistakenly believes that Joe is a new hire. We might say:

*Joe has always worked here.*

to mean nothing more than the fact that Joe is not a new employee. He has been here for some while.

If we want to say that Joe never slacked off when he was working at Acme Widgets, but always took his job seriously and gave it his best effort:

*Joe was always working when he was at Acme Widgets.*
/simple past/ means **perfect** or done. /always/ can be used in past form when we want to **emphasize** the event.

past progressive follows simple past.
for ex:
*I was reading a novel* when *he knocked the door*.
you could also say:
He knocked the door while I was reading a novel.

as long as I know, adverb of freq /always/ is not good to place in past prog. tense