I came across this quote while reading my devotional from June 9th (yeah, I'm slightly behind).
"Anyone who stops learning is old, whether at twenty or eighty. Anyone who keeps learning stays young. The greatest thing in life is to keep your mind young."
That's pretty brilliant, and a motto I hope to keep. The devotional had an interesting perspective, saying that we can learn so much from older Christians. God worked in previous generations' lives (see Psalm 44:1-3), and we can learn from older folks' experiences.