How McDonald's built up my mental resilience

Having a stutter and working in a fast paced environment like McDonald's was a challenge. When I first at, I was never told straight up but it was clear there were many concerns over my speech and having me working with customers. One clear sign was how people I started at the same time as were trained in everything included service within weeks, but I wasn't even taken out of the kitchen in months. Reading between the lines I was told I would never work with customers, never-mind get a promotion. For
a long while I adapted to that thought that I'd be stuck in the kitchen cooking chicken nuggets for good.
But then my mindset started to shift.
I was ready to take action and do something outside of my comfort-zone. So I asked, and asked, and asked some more until I was finally given chance on service. Months down the line I was primarily customer service, why? Because I was good at it and enjoyed it. It wasn't easy and I did face many challenges. I couldn't shout out an order number in a crowed restaurant so became the laughing stock for the next few minutes; once I had a block working the drive-thru and the customer thought the machine was broken to which I responded, "no I am," which they found equally as funny; always got the odd comment or joke, even from co-workers. One moment that stood out was when a man said "someone like him should never be allowed to work with customers." That was a real knock for my confidence, yes the manager did stick up for me but I still felt awful. Moments like that made me second guess whether I was good enough or not. I did have a lot of doubt not just about my job but about my speech overall. It was hard, very hard but to overcome it, I started taking the negative feedback and started using it to spur me on. Since then if someone tells me I can't do something, or I won't be able to do something, I'll do everything in my power to prove them wrong. Adjusting to this mindset helped me a lot. So much so, during an inspection the area manager labelled me "The best example of customer service he's seen in a very long time." That was a big moment for me. All this happened before I went on any speech course or had any way of controlling my stutter.
When I did come back from the Starfish Project, I had a voice. Although that seems a good thing, majority of people were used to me being the 'boy with a stutter' so basically I never spoke up for myself. When I did start to speak up, and was in training for a promotion (which at one point I never thought would happen), I got a lot of negative feedback from people. And it wasn't because the 'power went to my head' or I suddenly became a knobhead. It was because I dared to stop conforming, and started standing up for myself and actually taking responsibility. In short, I couldn't care less about their reaction. Even though I was trained and practically had the promotion, I handed my notice in and left.
Why?
Because I wasn't happy. I still hated it, if not more now because I became the person I've always wanted to be and had a 80% negative response. And I wanted more, so it wouldn't be right to stay. I'm very grateful to a lot of people I met there and the job taught me a lot, helped me grow, but at the end of the day you got to do what's best for yourself.
Moral of this story: Don't let anyone dictate what you can or can't do!