Why Do We Cast Our Crowns?

Let me share these facts with you. When God saves us and fills us with His Spirit, setting us free from sin, it is Him in us that is causing the remission of sins as He causes us to walk according to His commands (sanctification).

I will put My Spirit within you and cause you to walk in My statutes, and you will keep My judgments and do them.
Ezekiel 36:27 NKJV

In Him also we have obtained an inheritance, being predestined according to the purpose of Him who works all things according to the counsel of His will,
Ephesians 1:11 NKJV

for it is God who works in you both to will and to do for His good pleasure.
Philippians 2:13 NKJV

But by the grace of God I am what I am, and His grace toward me was not in vain; but I labored more abundantly than they all, yet not I, but the grace of God which  was with me.
I Corinthians 15:10 NKJV

For this reason we will cast our crowns at His feet. When we sin, that is our doing, but when we do good that is of God.

the twenty-four elders fall down before Him who sits on the throne and worship Him who lives forever and ever, and cast their crowns before the throne, saying:
Revelation 4:10 NKJV