God is love, and prayer centered on love is highly important in Christian practice. The second aspect is conviction (or faith). (See Ask, and it shall be given you.)
This isn’t meant to be understood in an abstract way, but a concrete, experienced way. For it to matter, it has to be real.
So, pray with joy. Joy contains love, and is a kind of enthusiasm. Hence, it contains both love and cultivates conviction. By praying with joy you connect with God more fully.
A recipe for prayer is to infuse joy into prayer, and then let go, letting God do his work. This recipe will increase both love and conviction in your prayer life.
How do you infuse joy into prayer? The first step is to ask God to come into your heart and mind. Then actively see joy in whatever situation you are praying about – don’t focus on what you fear, but a joyful outcome. ‘Love casteth out fear.’ Then let go, knowing God is working to align things and guide you in your actions to bring more joy into the world.
The point of prayer with joy is to bring more joy not just into your heart (which is highly important) but into the world outside.