It is a good question, and I'm sorry you are going through this. My honest answer is--I don't try to stay positive. My emotions change all the time, like the weather, and I'm used to that. I do, however, manage my anxiety (I was an anxious person before breast cancer and remain so after!). Try to see what helps--exercise. medication if needed, even just relaxing in ways you enjoy. Can you just accept that your ups and downs are inevitable as you are a feeling and caring human being? I will be thinking of you. Check in here any time you feel like it--I think most oral of us have experienced what you describe.