the flaw in my design

This is the second prompt from my final workshop… We were supposed to write about some kind of light that seeped through the cracks in our life, or something like that. Anyways, this is what I got!

My mind was guarded
by a fortress my heart built

Each stone selected
was strategically placed.

My walls stretched higher and wider
than a behemoth mountain range.
My shield was invincible
to the elements and assaults

Venomous words
would strike like weapons
but,
They couldn’t pierce
or grind it dow...