We can have sympathy with David, tired and unable to hide from Saul, but the plan he makes to escape to the land of the Philistines is founded in unbelief. He goes on to deceive Achish and ends up in the situation of Achish wanting him to fight against Israel. It all started with David feeling tired. In our sorrow we can do the solitary things. David failed, but God uses him. He moulds us for His purposes.