A Dirty Sponge

The brain is like a sponge in that they can both retain a lot of dirt. The brain retains a lot of negative thoughts, ideas, and memories. Every now and then they both need to be wrung out.

The ghosts of what we erase on a computer remain deep within the system, electronically etched into the hard drive. Similarly, what goes into the human mind can remain to contaminate it or to enrich it.