Lust corrupts your prayers, making them go unanswered. James says prayers asked amiss, driven by selfish motives, don't work. Hours spent praying mean nothing if your heart wants the wrong things.
Lust is such a dangerous thing because it can infiltrate into your prayer life. When you think of lust, you, you never think about prayer, but James is teaching us there's a concept of lustful prayers. It says you ask and you have not. Why? You ask and do not receive because you ask amiss. Man of God, spend 24 hours praying for the wrong things, it means nothing. Remember what I said in my poem, prayer is not measured by time or volume, it's measured by the distance between your heart and God's mind.
