Still, open are the questions of what defines "grit" and especially what defines "success" for every individual case. Goals have to be established in order to see these matters clearly.
Also, whenever you want to accomplish a long-term task, one must never disregard the matter of luck. It is often put aside when people write books about accomplishing things because it plays so great a role in life and they wish to dismiss it's power.
It hurts sales to admit that simple truth.