After I was dx'd the year I turned 21, I slipped into a terrible depression that lasted for about a year. I'm convinced, now, when you think about how much glucose the brain needs to operate correctly and how the brain is also the center for our emotions, that the changes one undergoes in the body during those early days of diagnosis, trying to get the blood sugar under control after who knows how long it has been out of whack, probably does cause chemical changes within that may effect one's emotions as well. I'm a strong believer in the body-mind connection.
Getting diagnosed is often a scary and lonely time. I had a similar reaction - at first, I felt like, okay, so it's diabetes, what now? It didn't feel like that big of a deal. But falling into a year of depression.... that was really horrible. If you can find a support group in person, I think that'd be a wise thing to do. I've been thinking about it more now than I ever have before in my 15 years with type 1. But also, having this and other online support systems can be very very helpful. My life experience is that most people don't know much about diabetes, or what they do know is of type 2. So if you can stay connected to those of us who have it too, that can only be of benefit to you.
I think a lot of my depression, although it had a chemical component, was also impacted by not having anyone in my life who understood what I was going through with the type 1 diagnosis. Diabetes is a weird disease in that you "look" normal, and it is therefore very easy to blend in and look like everyone else, though you may be feeling like utter crap inside. I spent a lot of the last 15 years pretending I was just like everyone else, which can turn into a kind of denial and lack of compassion for what it really going on within. I have seen time and again that when I deny my own health needs, everyone else does too. I think that if I had found a support group earlier, I would have been in a better state of acceptance and possibly wouldn't still be struggling so hard with my self image now.
Fifteen years ago, the internet didn't exist like it is now, with lots of social networking capabilities. Use this to your advantage! Cultivate some online community for yourself, like you are, especially now when your life has to adapt to this new set of circumstances. It is so normal to have feelings of sadness right now. Please remember to always be kind to yourself.