How is it possible?

Struggling to understand how it is possible to go from one end of the emotional spectrum to the other, one day to the next.  I am not doing anything different yet it seems i go from racing thoughts one day to slow and apathetic the next day?

My boss cornered me today. She knows something is wrong.  Luckily I was in my apathetic emotional state, otherwise I would have started balling and panicking at having to explain myself.  Instead I just came up with the excuse that my current position is no longer acceptable to me....which actually isnt an excuse.  I dont love my job anymore. Im not learning anything new, and unfortunately I know its mostly my fault. I used to take my work home with me, research everything I could....I like being so confident in myself and my knowledge that i never have to question if I have the right answer.  And if I dont know the answer, I pride myself on not stopping until I find it.  People come to me because they know I am good at what I do and they know I can get them answers. Now, I use all of my spare time trying to educate myself on Louisiana law and digging up any information I can find on these individuals that have the nerve to call themselves men.  This group of "men" have proven to be a disgrace to their "kind".  I have let my rapist take away what I love and I feel more than pathetic for that.  Eventually I may have to tell my boss what my real problem is when she wonders why I am disappearing so often on trips to New Orleans, but I will cross that road when I get to it.

After avoiding questions and explaining myself, I have the option of taking a new position.....and its tempting.  I can get back to the education part of my job....the part I miss most.  I will still get to work with the same fantastic group of people I do now, and a few new people too......the downside is my best friend and I will no longer be sharing a tiny office with a autographed picture of Mario Lopez from his Saved by the Bell years framed on the wall.  Im not sure how this will affect me.  Sometimes she was the only thing that kept me from panicking during work, just knowing that I could panic in front of her and she would just shut the door until I was done....not judging and not making me feel pathetic. 
Thats the thing,  I have no idea how my day is going to go.  Before I was raped, I knew what to expect.  I knew how I would handle situations that came up.  I was always calm.  I was the one telling people there is no use in panicking over something that isnt really in your control....
I think that with my new position, and being around new people, and being able to get back to learning, I may be able to keep the panicking under control.  Its strange, I find myself narrating my life, to myself, in my head.....basically like JD on "Scrubs"....I talk to myself in my head....i pretty much cant do anything without laying it out in my head first.....its actually pretty creepy.
Anyway, if anyone has the answer how it is possible to go from one emotional extreme to the other in such a short amount of time.....and what, if anything, can be done about it......it would be greatly appreciated if you would let me in on it.