Ashes can symbolize death. Our Savior brings such good news, but He suffered while He was here on earth so that we could know Him and have a relationship with Him. The Lord has given us so many things, and He has given us beauty instead of ashes.
Lent began yesterday, on what is known as Ash Wednesday, and reminded me of this verse. From what I have read, believers in Christ usually choose to make extra time in their day for prayer with God, time to serve others, or time to abstain from something. I think the purpose is that we turn our focus on the sacrifice of Jesus Christ, who went through the pain of death for us so that we may know Him.
Through this memory of Christ, we find joy. This is because we know that because of Jesus' death, satan cannot use law or sin to keep us from God. We are able to live and have a relationship with Jesus Christ, which brings incomparable joy (for more on this, I recommend reading Seeing and Savoring Jesus Christ by John Piper).
The joy that comes in knowing Christ and glorifying Him is so much better than things on earth. I pray that we remind each other to steer our thoughts and conversations towards Christ, Our Savior.
"Praise the Lord, all nations! Glorify Him, all peoples! For great is His faithful love to us; the Lord's faithfulness endures forever. Hallelujah!" (Psalm 117:1-2, HCSB).