It’s the start of a journey and it’s not half as bad as some other conditions that people are unfortunate to be burdened with. When I was diagnosed at 22 my doctor told me, “The more you know about diabetes the longer and healthier you will live”. Now 45 years later I still go by that and believe that I haven’t done too badly. We are much better equipped now to deal with our condition. Never stop learning. Follow your interests and passions. You will find that life ahead is a lot brighter and more colourful than it would seem at the moment!
Don't worry to much ; just do what the doctors require you to do and then you will know what you should do and what you should not do. It's all a learning curve which you will learn to "drive" for a better live and live longer as I was diagnosed at 14 and now I am 73 ,with only a few small problems which are not bad for my age?
Maybe they were already doing that? Simply saying 'stop worrying' is dismissive in my opinion, this person has suddenly been told they have a lifelong disease which requires constant monitoring and attention to a degree that is life changing. Stop worrying?, it's not just a question of a 'diet only' approach (which I know can be hard), it's everything else that comes with being insulin dependent.
Just back from a work trip and saw your reply. I didn't intend my post to be dismissive in any way. That said, stress raises BG levels and worrying about our condition isn't helpful. Positive action to control BG is far more productive than worrying.