Demotivated

Can constant demotivation lead to adverse effects on a person's mind that his strengths turn into his weaknesses?

I feel something similar happening to me. As a writer and editor in my previous organisations, I have always been passionate about writing clearly and creatively. But off late I have observed that I have become careless about it. I go blank when it comes to producing ideas, its more like something clouds my thinking and and I don't feel motivated anymore, which is reflecting in my day-to-day job. And I hate it. Something that I could boast of, was now something that I am ashamed of.

The cause of demotivation, well give it a simple guess! B-O-S-S!!!

A manic person in her personal life, she passes on virus to me. Never happy with anything, wanting to drive a single man army and taking credit for everything is her forte. So when I see that everything I do to the best of my efforts is negated all the time...I don't care about it. I don't put my passion into it. But I want to overcome this. Because writing is something that I cherish and I don't want it become a hassle. Please help!