"If my People who are called by my name shall humble themselves and pray, and seek my face, and turn from their wicked way, then will I hear from heaven, and forgive their sin, and heal their land. "
Repentance is preliminary to prayer. I do not deny that God may answer the prayer of someone who is still in rebellion against Him. I am certainly not in control over what God chooses to do. But the great problem is with what that person desires. Such persons may ask, even demand that God leave them alone. And He may ultimately answer that prayer. C.S. Lewis noted that the gates of hell are locked from the inside.
Frankly, I am relieved that God can be trusted not to answer prayers that are against His will. All joy, all peace and all blessings are in God's will. Note the word of repentance in this verse. It does not call us to repent of wicked deeds. That is an important part of repentance. But this verse calls us to turn from our wicked way. This is talking about the direction of our prayers and our entire lives.
In this light repentance is also a process. The more time I spend in God's presence, praying, prayerfully saturating myself in His word and obeying what He tells me, the more He turns my heart in His direction. He implants Himself in my heart and mind and will. He changes what I hunger for Him to do in my life and in the world around me.