Feeling Undervalued After Learning a Coworker’s Salary—Did I Negotiate Poorly?

About a year ago, I left an MBB firm to transition to another industry because I was really unhappy. When I made the move, I took a very small pay cut (my current job thinks I’m being paid the same—long story).

I recently found out that someone two years younger than me, who joined the company a couple of months after I did and was being paid less in their previous job, is now earning 11% more than I am. I’m not sure how to feel about this—was it poor negotiation on my part?

I don’t really know what to do. I was feeling super motivated at work because I’ve been performing well, but now I feel like I’ve failed, and my career is going downhill.