Self boycotting

During my three years of psychotherapy, my shrink tried and tried to help me avoid this damaging tendency of self-boycotting myself.
At that time, I thought I could overcome such need, but yesterday I realized I didn't. For the last months, I thought that my academic life was great. A lot of hard work which was giving its fruits. However, yesterday I started to think about the unthinkable. I'm not going to get my degree neither when I wanted, nor as I imagined.
I'm having a little tiny stone on my way which is in fact a big mountain for me. Since anxiety has become my worst disease, the idea of not having passed one of my exams is just killing my soul.
I know for sure that I'm wrong. I should take this as it is: just a little tiny stone on my way...but I can't.
I deny the idea of thinking too much about something, because in general terms, everything ends up being something one hundred percent different. But in terms of getting my degree, I think I've been dreaming for a long time. And I shouldn't. This is not due to a high level of negativity in my blood, but because I started to believe in the idea of dealing with things the best way I can at the precise moment in which they happen to me.
I wish I could be different in this aspect, I wish I didn't have this tendency to self-boycotting, but what can I do? Everthing has been so difficult to get, that sometimes I cannot believe that my life is a great gift. I cannot understand why God has given me so many good experiences to be proud of. There's something wrong when the world becomes a perfect rounded circle.
Someone said yesterday, that when you really want something, and you think about it, it is almost certain that you're going to get it...I don't know if I'm completely wrong, but I don't think so. My experience tells me that it's not that easy. It's not only a matter of sending "good energy" and receiving back your wishes accomplished...
I should be a rabbit mum, full of children if that was the case.
I don't know, I don't want to be pesimistic, because I know that my friends are going to tell me off, but I don't know what can I do.
Today my mother was very upset when I told her about my exam. She almost shouted that I was an intelligent person, and I shouldn't be so worried until I have certainty. I don't know...maybe she's right. But my experience writing essays in this subject hasn't been encouraging. Almost every written production that I presented was a failing mark.
Which are my possibilities to pass this exam?...
Almost zero
Time will say.