Look at my second paragraph. Key words are fluidity, melt, mold, all references to liquid forms. Even the word run itself. Solids do not. Maybe another reason why we run.
Life is hard.
There are stresses at work, and sometimes, we lose our jobs due to no fault of our own. Relationships are tough. Even the most solid ones have bumps in the road. Children are a challenge. The may provide our greatest joys, but also cause us our deepest despairs.