What did the waterfall and water cube mean?
you can think of the cube as sort of a lens through which you see the world while dealing with depression. When you make it out the darkness and can see the world as it truly is, but it's good to remember the experience you had before and the way it affected you. Surviving depression, to me at least, doesn't mean to live completely without the negative emotions. Rather, it's more about understanding where these feelings come from and being able to adequately respond to and live with them.
I hope that makes sense! && thanks for playing :)