Hi Paul!
Good Morning, well, it's morning here I don't think you are over-reacting to the diagnosis, it just sounds like you may be a bit overwhelmed. You will learn to deal with the roller-coaster rides, and some days you won't have them at all. I was diagnosed BPD 19 years ago; some days I still feel like it is brand new and I struggle to deal with it. But this illness is not you, it is just something you struggle with. The fact that you are starting on a physically healthy program will help your mental health, too! Having a pet helps a bunch!
Good luck to you! Come back and talk to us!
Autumn