Metaphor is the bridge between the images and emotions of the subconscious and the language of the conscious; the former the deep and powerful under sea currents and the latter the more obvious waves upon the surface.
The bulk of our thinking is in the subconscious, in pictures and emotions. The rest, our conscious thoughts are in language for the most part. And so metaphor is a bridge between the two, a way for our whole brain to communicate internally to the self and externally to others in a truthful way. Thus we would do better to embrace metaphor and the language of poetry more fully in our speech and feel the deeper wisdom it holds.
He shouldn't make promises he can't keep, they both knew that. Dustin shouldn't water him with false hope and plant him in a soil full of lies in the hopes of him growing whole again. It was wrong and unfair to both of them. Dustin still did it though and Steve still believed it.