Seems it is like activating a specific and concentrated aspect of psyche to have a strength or other abilities in a time of need.

In the case of my dream and switching to Superman, I see Superman as source of great strength of which I put part of myself into it for use at later time. Seems so. Like for an example, the Sandman or Dreamer in comics did put a lot of his powers into a ruby stone as being tool of his own for governing dream realm. Unfortunately, it got stole and used for bad deeds by someone. When the ruby stone broke, all powers returned to Sandman / Dreamer, thus making him more powerful than before.

But though, there could be a very good reason for making a ruby stone (ie Tool of choice) for purpose and limitation reason, but it has risks and consequences nevertheless (eg. got stole and used for evil deeds).