I love this promise! Consider the "cloud of darkness" as ones inner feelings during times of depression. I know this works - I have put it to the test more than once.
"What shall we do, that this cloud of darkness may be removed from over-shadowing us?" (v40)
"You must repent, and cry unto the [Lord], even until ye shall have faith in Christ, who was taught unto you..., and when ye shall do this, the cloud of darkness shall be removed from overshadowing you." (v41)
"... they did ..." (v42)
"the cloud of darkness was dispersed from overshadowing them ..." (v43)
"... and they were filled with that joy which is unspeakable and full of glory." (v44)
"And the Holy Spirit of God did come down from heaven, and did enter into their hearts, and they were filled ...." (v45)
"Peace, peace be unto you, because of your faith in [Him]." (v47)