A Lot to Unlearn

Although God could instantly transform us, he has chosen to develop us slowly.
Why does it take so long to change and grow up? There are several reasons --
We are slow learners. We often have to relearn a lesson forty or fifty times to really get it. The problems keep recurring, and we think, "Not again! I've already learned that!" - but God knows better. We need repeated exposure.
We have a lot to unlearn. Many people go to a counselor with a personal or relational problem that took years to develop and say, "I need you to fix me. I've got an hour." Since most of our problems - and all of our bad habits - didn't develop overnight, it's unrealistic to expect them go away immediately.
Growth is often painful and scary. There is no growth without change; there is no change without fear or loss; and there is no loss without pain. We fear these losses, even if our old ways were self-defeating, because, like a worn out pair of shoes, they were at least comfortable and familiar.
Every change involves a loss of some kind: You must let go of old ways in order to experience the new.

The Lord your God will clear away these nations before you little by little. You may not make an end of them at once, lest the wild beasts grow too numerous for you. (Deuteronomy 7:22 ESV)

An excerpt from Rick Warren's Daily Devotional Reading