How do I deal with wondering if my career was the best use of my mind?

You can run a category like its own business, which takes a sharp and capable mind. And quietly you wonder whether optimizing procurement was really what that mind was for. That question is not ingratitude. It is a thoughtful person taking stock, and almost everyone who is good at their work meets it sooner or later. Consider this though: the value of your work is not only in the subject. It is in the thinking itself. You learned to see systems, find waste, make complex things run well. That mind you built is real and portable, and the fact that you can even ask this question shows how much of it you have. You do not have to settle the whole meaning of your career today. You can just aim a little of that mind at something that feels worth it to you, inside work or outside it. Mentor someone, take on a harder problem, or use your skills for a cause you care about. Meaning is often less about the job and more about where you point the ability the job gave you.