Faith and repentance are heavily interrelated. Faith in Christ means we sincerely believe His commandments outline the right way to live. If we sincerely believe that, we can't help but want to repent. Repentance is changing ourselves so that we follow His commandments more exactly.
As we believe ever more strongly in the ways of Christ, not repenting causes increasing turmoil in our own hearts and lives. To have a strong belief in the true way to happiness but not live accordingly is torment. Faith without works is not only unprofitable, it increases misery.