This is a question I spent some time reflecting on after I was reading in Isaiah 43 recently. There's a few verses in that chapter that are more well-known and I've heard quoted often. They're powerful words, but I realized just how powerful when I read a couple of verses before them alongside them.
"This is what the Lord days -
He who made a way through the sea,
a path through the mighty waters,
who drew the chariots and horses,
the army and reinforcements together.
and they lay there, never to rise again,
extinguished, snuffed out life a wick:
Forget the former things;
do not swell on the past.
See, I am doing a new thing!
Now it springs up, do you not perceive it?
I am making a way in the wilderness
and streams in the wasteland."
The last couple of verses are the ones most commonly quoted, but when I read these verses all together I was struck by the thought sin them.
In describing who the Lord is Who is speaking, Isaiah is remembering how God led Israel out of Egypt and defeated their enemies. When they were in the an impossible situation and defeat seemed almost certain, God made a way out for them and defeated their enemy.
This is something they needed to remember. But, Isaiah also warns of a danger here. When he asks if they are perceiving the new thing the Lord is doing, he points out the danger and the reason why he is declaring that God is doing a new thing. There is a danger that in remembering how God has acted in the past, they would not see what God was doing now, or they would try to limit what God was doing now.
We face that danger in our lives. We need to remember what God has done for us in the past. That's what gives us hope and confidence that God will act now on our behalf again. But, we can too easily become so focused on the past that we miss what God is doing now. Or we can try to put God in a box of "this is how God does things" and resist Him when He tries to do something new.
In our remembering how God has acted on our behalf in the past, we cannot stop looking ahead for the new things He is doing and wants to do. Our remembering forms the basis of our belief and our confidence that He has a plan, but we cannot become so focused on it that we miss the new thing God is doing.