"It is Done!"

"And He who was seated on the throne said, 'Behold, I am making all things new'. Also He said, 'It is done! I am the Alpha and the Omega, the Beginning and the End. To the thirsty I will give from the spring of the water of life without payment. The one who conquers will have this heritage and I will be his God and he will be My son.'"

I used to understand "It is done!" differently. Now I'm able to see it as an echo from the cross.

He is also, "The Beginning and the End." I believe this could possibly be reference to our salvation and sanctification. "From faith to faith." It is Christ through and through and there are no grounds for boasting.

I'm still wondering what this means in Revelation19:8:

"It was granted to her to clothe herself with fine linen, bright and pure- For the fine linen is the righteous deeds of the saints."

My guess is that the righteous deeds are our deeds done in faith? In other words, allowing Jesus to live through us. Because, as it's written, "Apart from faith, it is impossible to please God".

Anyone have any other insight on these two passages?