When Christ died for us and made us new, He purchased the redemption of our emotions.
Instead of anger driving us to self-centred actions to harm others, it can now be used to fuel self-sacrificing actions to protect and care for others.
Instead of delighting in sinful actions, we can now honour God in our joy and when we don't feel joy. Joy is not our god or our hope - Jesus is. And in His presence there is fulness of joy forever.