Realism is, in it's pure distilled form, is an anathema to my beloved romanticism. Sure it can bring you back from both swings from overly pessimistic to overly optimistic states, but I couldn't see purposefully striving for that pure balance at 50% as any less tragic than seeking out a completely empty or full world view.
A more eastern philosophic look at this question would throw away the glass metaphor entirely, and perhaps set up an image of a person floating in the ocean, out way past the breakwater, unable to fully see how the waves interact with them from outside of themselves, either looking up at a looming wave or down on the displaced trough from what appears to be the top of the world. So.... which perspective would you prefer, grasshopper?
Grasshopper:
Me: