I think it’s important for the Believer to know his lost estate before saved by God. The only reason I think it’s important is because Paul seems to think so as he reminds the Ephesian readers of this in the first three verses of chapter two.

Let’s be honest. We’d all like to forget our past, especially the blunders, the mistakes.  I recently had someone remind me of something I said years ago, and my first thought was “Really, that’s what you remember?” It wasn’t even a bad thing.  When I think of my past, I’m glad there are things that don’t come to mind.  Paul, however, seemed to think it was good to remember who we were and in what condition we were in before we met Christ.

Eph 2:1-3 ESV

And you were dead in the trespasses and sins 2  in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience— 3 among whom we all once lived in the passions of our flesh, carrying out the desires of the body and the mind, and were by nature children of wrath, like the rest of mankind.

Read what Charles Ryrie says of our depravity:

The scriptural evidence provides the basis for what has been commonly called total depravity. Depravity means that man fails the test of pleasing God. This failure is total in that (a) it affects all aspects of man’s being and (b) it affects all people.

Negatively, the concept of total depravity does not mean (a) that every person has exhibited his depravity as thoroughly as he or she could; (b) that sinners do not have a conscience or a “native induction” concerning God; (c) that sinners will indulge in every form of sin; or (d) that depraved people do not perform actions that are good in the sight of others and even in the sight of God.

Positively, total depravity means (a) that corruption extends to every facet of man’s nature and faculties; and (b) that there is nothing in anyone that can commend him to a righteous God.

Total depravity must always be measured against God’s holiness. Relative goodness exists in people. They can do good works, which are appreciated by others. But nothing that anyone can do will gain salvational merit or favor in the sight of a holy God.

(from Basic Theology, Copyright © 1986, 1999 by Charles C. Ryrie.)

I think it matters that we understand this because of the next two words in the English text: But, God.

It seems to be possible to lose the wonder of God when we forget who He is and what He did for us, in our place.  We were lost without Him. We sinned.  Gen 3:6-13; Rom 5:12; Rom 3:10-12, 18, 23, 24

But God.

Eph 2:4-7 ESV

4 But God, being rich in mercy, because of the great love with which he loved us, 5 even when we were dead in our trespasses, made us alive together with Christ— by grace you have been saved— 6 and raised us up with him and seated us with him in the heavenly places in Christ Jesus, 7 so that in the coming ages he might show the immeasurable riches of his grace in kindness toward us in Christ Jesus.

Here Paul sums it up in one verse: Rom 5:8

You can listen to a full sermon on this passage here.