How do you keep from forgetting Scripture after you've memorized it?
I don't. But practically, what can you do to keep it as long as you can? There is only one word. Review.
Review, review, review. There is no way to memorize Scripture that keeps you from losing it. Some people don't lose anything. Some people have traps in their head that just hang on to it. But only 1 in 10,000 people can do that. Average folks like me have to work real hard to memorize the first time, and then recurrently review to keep it. So I memorize verses every day, and I forget them every day.
This morning I re-memorized a verse. I finished Deuteronomy and ran across a verse that I memorized years ago. Maybe I memorize it once a year, because I read the whole Bible once every year.
The verse is Deuteronomy 33:26. "There is none like God, O Jeshurun, who rides through the heavens to your help, and through the skies in his majesty." So, I've got it memorized. I probably will forget it in a week. That verse is hard for me to remember.
I've memorized that verse probably five times in five years. I forget it because I don't use it as often as some verses. So, I jot it down on a little piece of paper and carry it in my pocket, pulling it out during the day once or twice. If I try to nail it so that it is useful for me over the long haul, I keep it and review it.
A practical thing I would suggest for people to do, is decide what cluster of text they want to always be at their disposal. For me I could name Psalm 46, Psalm 23, Psalm 1, Romans 8, 2 Corinthians 5:21, a cluster of texts surrounding justification, 1 Peter 4:11—"let him who serves serve in the strength that God supplies, that in everything God may get the glory through Jesus Christ, to whom belongs the dominion forever." This is the most quoted verse as we move into worship at Bethlehem.
So for my soul, for the warfare of my life, and for ministry in hospitals and counseling sessions, I want a cluster of texts at my disposal. Decide what those are, put them on a piece of paper, and review them until you have them down. I'll give you a little story.
My first or second year of pastoring I was called to the hospital—quickly. I went without my Bible. Rollin Erickson's wife just had a heart attack. I walk into a room of probably 20 family members that didn't know if she was alive or dead—as she is in surgery. Rollin gave me a big hug and said, "John, give us a Word from the Lord." Now, if I had my Bible I would have opened it to a Psalm or something. I didn't have my Bible, and for whatever reason at age 35 my mind went blank.
I felt so humiliated. It was horrible. Here are 20 people, and the husband of a dying woman says, "Give us a Word from the Lord." I can't even remember what I said. I probably said, "Let's pray," and tried to paraphrase some Scripture. I went home and got on my knees that afternoon. I said, "Lord Jesus, that will never happen again." I opened to Psalm 46—"God is our refuge and strength." I have been able to quote Psalm 46 verbatim for the last 28 years. I decided that Psalm 46 is going to be in my head because it is so useful all the time.
The answer is, review. But don't try to do that with every verse you learn. You should be learning hundreds of Bible verses by heart, and forgetting 90% of them. But then you get to them again and relearn them, and they are still with you because you learned them once. Somehow they will function to get out into your life.
But really nail down a cluster of soul strengthening words.