I learned about mood swings and diabetes from one of my staff, a few years back. He didn't know how unpleasant he was to work with. I took him aside for an attitude discussion and the impact on his team/customers. As a result of that conversation I was introduced to diabetes and its impact on emotions, without the person knowing how they were reacting/behaving. (I did some research and worked out a plan of action for him that improved both his reactions to his fellow workers, and customers, successfully.)
When I was diagnosed with T2 last May, I recalled those conversations and hoped I wouldn't be impacted. But I was - as my loving and patient hubby pointed out on many occasions.
Now I'm (hopefully) more aware of my reactions/behaviours - and when I hear myself being rude or negative, just act/pretend to be cheerful and upbeat.
I've now got my hubby fooled as he now rarely knows when I'm moody/depressed (and he watches me like a hawk as he's terrified of the negative impacts of diabetes, and is determined to keep me alive and healthy indefinately!)
For me it's being very aware of mood swings, and to be aware of others' reactions to me, and modify behaviour accordingly. Sometimes it's a challenge, as last weekend, where I had to keep forcing a happy smile all day, being and saying positive things etc. But then isn't some of living life acting? Just for those of us with the mood issues, it means a little more acting that normal.
I wish you the best in this challenge - one of the smaller ones in the journey that is diabetes.