Why does Ralph feel that life is an improvisation?

It is first helpful to examine the whole quote,

"He found himself understanding the wearisomeness of this life, where ev- ery path was an improvisation and a considerable part of one’s waking life was spent watching one’s feet."

Ralph is learning that being leader is not easy. Simply doing the right thing is not enough. He must constantly be on his toes playing politics. He must impress and spin his information. He must constantly be on guard from attacks on his leadership by improvising his plans at a moments notice. Ralph is no longer a child.