OK, lots of virtual hugs. The first thing to know is that you are not alone. Many/most of us T1s have been where you are at some point in their lives. It's very easy to fall off the diabetic wagon but you have to remember that it's a marathon and not a sprint (oops, sorry for the tacky metaphors) and there's absolutely no point in agonising about poor control and possible long term complications when the most important thing is to get back in control of your diabetes and your life. (Sorry, you haven't said you're worried about complications but I know that's the first thing that comes to mind for me when I worry about T1 and less than stellar blood sugars.) As
@Knikki said, you've done it before so you know it's possible to manage your diabetes.
1) Do you have any friends/family/other T1s that you can talk to in real life. (I was lucky in that my mother was T1 so my family were always very understanding).
2) Getting back on that wagon. Some of the things that people do when things go wrong is miss injections/stop testing/stop going to clinic/ stop caring about matching insulin to carbs. (When I was a school age teen I used to spend Wednesday evenings in the library and have a milkshake and a doughnut before going in - this was pre glucometers but I am 100% sure that my blood sugar went sky high after that "snack" and I just didn't think about it.) So, make an appointment with your DN and take in your food/insulin/activity diary as suggested by
@Juicyj. I'm hoping you've been taught to modify your insulin doses but if not then now is a good time to ask for help (everyone seems to swear by DAPHNE courses).
3) Work. Is there anyone you can talk to at work about your diabetes? Or are you hiding it? I personally found it very helpful for everyone to know about my T1 (in one job with a small company one of my colleagues was also a T1!), just so that they knew about hypos.
Good luck. You can do it. As your blood sugars improve so should your mental health.