I hadn’t really heard the phrase “joy-based repentance” before, so it made me really think. To repent is to sincerely regret and feel remorse, and ultimately to turn away from the sin. The feelings that lead up to a repentant heart aren’t really joyful - they’re full of sadness, anger, and shame. But the act of repentance itself, is receiving God’s grace and forgiveness, having Him wrap His infinite arms around you and tell you that Jesus washed that sin away. That’s a pretty wonderful thing, and one to rejoice about.
When we repent only out of fear of the consequences, our heart doesn’t experience the same thing. It doesn’t mean that it can’t be genuine, but it can make us feel “less than” and inferior because we aren’t letting ourselves receive Gods grace and mercy. The fear causes us to continue to condemn ourselves, even though we’ve already repented - it’s a vicious cycle, and it’s not what God wants for us at all!