The Merriam-Webster definition of grit is the "firmness of mind or spirit: unyielding courage in the face of hardship or danger." Not the definition of a friend used to describe his dissatisfaction of a contemporary as "the grit in the gears of progress." Your personal definition has probably matured over the years as you think beyond cramming for a school final.
We don't run from bears and saber-toothed tigers, so our biggest challenges are self-imposed. We claim to do hard things by skipping a meal and at the first temptation the donut gets dropped into the face trap. Skipping a meal is a daily occurrence for much of the world, and it is hard to justify this as grit. The second element is thriving in these conditions for a sustained period. It is clear that long-suffering is a component of grit and runs counter-culture to our give-it-to-me-now, always-on society.
The perseverance to stick it through to the end is critical when the project is necessary. Each minute of your life is invaluable, and your passions demand your time and effort to make the dream a reality. Pursuing your first muscle-up, achieving a deadlift personal record or helping struggling kids, over years, place well on college entrance exams, require grit to submit the final product and await a verdict. Pushing through the brain fog to produce good work, despite the long nights and little sleep produce grit.
What is your history with grit? How does this inquiry challenge you and encourage you? What challenge did made you appreciate grit? Who is your real-life example of grit?