“Thy word have I hid in mine heart, that I might not sin against thee.”
The typical application of this verse goes like this, “You should memorize scripture so you can defeat sin when you are tempted, much like Jesus did in the temptation in the wilderness.”
I guess that’s OK, if it worked for Jesus there must be some credibility to this application. However, I think Psalm 119:11 is making a much larger point.
Psalm 119 uses the term “heart” often and mostly the term “whole heart.” He is talking about allowing God’s word to overtake his heart, to consume it.
The heart is deceitful, the only answer to this problem is to give it over to God who can make in you a new heart, one filled with His word, will, desires, thoughts, intents, etc.
Thinking that having a few verses rolling around in your head is going to protect you from sin is not the idea. Mentally rubbing a few verses like a lucky rabbit’s foot probably won’t carry you through.
Having God’s word overtake your heart, to live by faith, by hearing God’s word, is what allows us to overcome the world.