Do you sometimes wonder if you're "losing it"? I know I do more often than not. It's happening much quicker than I expected!! LOL Doctors say that in most cases mindless hours in front of the television, avoiding intellectual stimulation and exertion, result in the shrinking of our mind's capacity, including our memory.
When you let your mind "veg" and don't stretch it with thoughtful reading, rational thinking, intelligent analysis and conversation, it loses plasticity and becomes old at any age. On the other hand, if you challenge your mind regularly, your brain gets younger as you get older.
God promises that if you meditate on His word daily you'll become "like a tree planted by streams of water...which yields it's fruit in season and whose leaf does not wither. Whatever he does prospers." (Ps 1:3) Don't let your mind "wither", exercise and strengthen it by studying the Scriptures!