When you say someone "can't see the forest for the trees," you imply that they are overly focused on details to the point of short sightedness. It is the idea that we can become so focused on what is in front of us that we cannot see the larger picture. 

This morning we’re studying problems (what we see) and promises (what God sees). God’s people had a lot of problems back then. (Maybe today also?) But God also gave them great promises, promises to which we too can cling.