Such fluctuations in mood are common especially when one is under stress. It is better to consult a mental health professional for better management of the problem.

Pls cry alone in a room. This is called cry therapy,after crying u ll become normal  the benifts of cry therapy I have put 5 yrs ago iny blog go through and find its benefits http://mindcounselling.blogspot.in/p/dr-sunderam.html?m=1

I can totally understand what you are feeling. There are times when thoughts over power is and we feel slightly negative at such a time we try and fight with the thoughts run after them and end up giving extra focus I know it's easier said than done, but with treatment you will be able to distance yourself and gain back positive control. So I strongly suggest you visit a Psychologist and if need be you can be referred to a Psychiatrist. Start this you will feel better soon. We are there to help you can also contact me for further queries or treatment.

Coming out of that vicious circle is bit challenging. This can be handled by understanding your strengths and weaknesses. Many a times,  we tend to cling to our weaknesses instead of appreciating our strengths.