In context, this verse is speaking of the person whose strength is the LORD. So it makes perfect sense that a person whose strength is God would go from strength to strength, like a kid playing on monkey bars and swinging from one bar to the next. Each bar is pretty much the same as the one before. God’s strength is likewise invariable. His strength is the same yesterday as it is today and it will be tomorrow. Like the monkey bars in the illustration, God’s strength supports the person who is dependent on it from one place to another, provided that person holds on and reaches for the next bit. Neither God’s strength nor the bars in the illustration remove themselves from the reach of the person looking for them — they are exactly where they were the moment before and where they will be the moment after. And both God’s strength and the monkey bars have a side on which you start and a side you are (generally) trying to get to.
A few centuries ago, a preacher (Jonathan Edwards, I think) wrote out a sermon called Sinners in the Hands of an Angry God. To let my geek flag fly: Preacher used sermon. It was super effective. In that sermon is a thought about a sinner held out of Hell and the grave by something akin to wet tissue paper which left the sinner every moment exposed to certain death. That illustration applies to the sinner who has not made God their strength. For those who believe, we remove the threat of Hell and substitute a quagmire we call Sin. Going back to the monkey bars illustration, the dirt below the monkey bars is a morass due to rain just before we came to play on the bars. Somehow, some way, the bars remained dry and perfectly wonderful, but the muck and mire underneath — that nastiness is especially nasty.
There are two ways I can play on those monkey bars. One, I can swing from one side to the other, staying reasonably clean and free of muck. Two, I can let go of the bars and drop into the mire below. There are likewise two ways I can approach the journey from the place I accepted Christ to Heaven (which I am substituting for the reference to Zion in the psalm). I can hold on to God’s strength in this situation and reach for His strength in the next — sort of swinging from strength to strength from here to Eternity — or I can let go and try to somehow stay clean. There are two parts to the equation and I need to be mindful of both: God’s strength (the bars) and my grasp. God’s strength cannot sustain me if I do not hold onto it. But His strength is always available for me to reach out and take hold of.
Meandering blog post is meandering. Let’s bring it back to something resembling coherence.
Those who rely on the strength of God go from strength to strength in much the same way a child playing on monkey bars goes from bar to bar. The person who relies on God’s strength is responsible for reaching out and taking hold of the next bit of strength much the same way as the child reaches out for the next bar. The person who relies on God’s strength will get from wherever they begin their journey to Heaven (Zion) to [appear] before God. The child on the monkey bars will get from one side to the other just fine, so long as they trust the solidity and strength of the bars and keep reaching for the next one. As the temptations come, let me swing from bar to bar; go from strength to strength and get through the temptation clean.