I can relate. When I got my first full time office job it felt like forced labour. I couldn't believe I would have to do this 9-5, 5 days a week. After the rhythm of uni life it's particularly draining. But telling yourself to man up is the last thing you need to do. Anxiety and stress has nothing to do with weakness; just because other people take it without a wince doesn't mean you should. Those people are either robots, with no emotional, intellectual or aesthetic life, or they've learned to acclimatize themselves to the rhythm of it.
And it doesn't have as much to do with personality and stress capacity as it does with health. What you're feeling sounds physiological; so many more life problems are than people imagine. If you're pouring near indigestible empty calories into your body, not exercising, and not getting enough sleep, you're eventually going to burn out.
I think you just need to put some work into your health. At uni you can do whatever you want to your body and sleep it off in class, but in the work world you have to take it seriously. Try to stop smoking, if you do. Easiest thing? Take out gluten, dairy and almost all sugar, even fruits. It sounds miserable but it's really not that big a deal. I promise you it will help your physical anxiety, make you feel fresher, more awake, energised and happier in just a couple weeks. And if you exercise, do meditation, you'll cope so much better.
That will make everything easier. After that, if you're still not able to cope with it, don't force yourself. In your 20s it's far more important to be happy and experiencing as much as you can than holding yourself up to ludicrous career standards. Get a part time job you enjoy, relax as much as you can, take care of yourself and try new hobbies and interests to keep yourself busy, don't just sit around and watch Netflix. If you're on the stress/anxiety continuum you need to get off and recover, take care of yourself, or you'll burn out. Nothing is worth that, trust me.