Because the old is better
We develop preferences. I heard a counselor say they are discovering that much of our personalities are already formed at birth; what is developed through nurture are our tastes and preferences, our sense of humor.
Falling back on "comfort food" when you are stressed (after all, 'stressed' spelled backwards is 'desserts'...) and being able to rely on old friends when you are in distress, these seem innocuous if not a source of relief.
The question is, when do our preferences hold us back? When do we fall into unhelpful, if not harmful and destructive patterns, get stuck hanging onto old glory or old hurts, identify with the past, whether it was ours or someone else's, out of pride or defensive fear? 'That's just the way I am.'
Jesus said: " “And no one after drinking old wine wants the new, for he says, 'The old is better.'” (Luke 5:39 NIV)
The challenge is figuring out what we need to hang onto, and what we need to let go in order to grow. Old sources of pride will isolate and hold you back; old roots of fear will cause you to wither and shrink; old sources of relief become addictions. (Also, these bodies just get old. Try to do the things you did as a kid results in wrecking yourself. There's a reason professional athletes over 40 are rare.)
"Therefore we do not lose heart. Though outwardly we are wasting away, yet inwardly we are being renewed day by day. (2Corinthians 4:16 NIV)
Being transformed in our souls, made more and more into the likeness of God's Son, re-created by the Holy Spirit of God according to the Word of God - our heavenly Father wants not what just feels better from our memory, but what will be best forever.
"He will wipe every tear from their eyes. There will be no more death or mourning or crying or pain, for the old order of things has passed away." 5 He who was seated on the throne said, "I am making everything new!" (Revelation 21:4 NIV)
Let Him work something new in you.