The phrase "one's sheer determination" means a person's unwavering and strong commitment to achieve their goals, regardless of any obstacles or challenges they may face. Full definition
He achieved all he has done through sheer determination and grit. (sbnation.com)
But guess what, you learned by sheer determination. (remonline.com)
You arrive at work after a relaxing weekend with your batteries fully charged and a look of sheer determination in your eyes. (growthengineering.co.uk)