So sorry you are feeling like this @beyond . I’m also a Nurse and you would think it would make things easier but sometimes it isn’t good because you know of everything that might possibly go wrong however remote. You might benefit from doing a Moving Forwards Course - ask your BCN or look into it on the main site here .
As for being positive - well if people can be then good for them but I can remember snapping at my friend when she told me to think positive - you feel how you feel and it takes time to put yourself back together mentally and adjust to physical symptoms as well after what you have been through. If you had been in a car crash instead of having cancer would you be putting pressure on yourself or feeling pressure from others to think positive and snap back to normal ? Somehow I doubt it.
It will take time to work through your anxiety meanwhile make sure that your clinical team know about your symptoms in case there are treatment options . Xx