Is positive thinking really important for the success of a casting? I came across this concept in occult books and heard from people around me that positive thinking actually helps good things to happen to them. But in my case it always yields negative results. If I EVER have a positive hunch I am sure it will go bad even to a measly extent- as I have come to learn from my past experiences.
There is a misunderstanding that often occurs when people think of "positive" and "negative". Positive doesn't have to be "good" but simply progressive energy. Think of it like math. A "positive" number adds and a "negative" number takes away. I might get more flat tires and that would be a positive increase but it wouldn't be "positive" as in a good thing.
Positive thinking in regard to casting has to do with being in the right place spiritually and mentally to produce the energy needed. Some books have worded it as you have to "believe" that it will happen and this might be closer to helping people understand what we mean by "positive".
Another example that almost everyone can relate to would be that feeling you get in the pit of your stomach when you "know" you can do something. Everyone at some point in time in their lives will feel this "I can do it!" feeling. Sometimes its evoked by music or by revelation but everyone feels a surge of energy. This is positive. Another (all to common) feeling is anger. Everyone has felt that anger boil inside them and make them feel far more powerful than they are physically. This is also positive energy. Both energies can fuel a spell but "dark" or traditionally "negative" emotions such as anger and hate will meld into the intent of the spell and make it something evil.
What you are talking about with the positive thinking isn't positive thinking but heightened expectation that usually doesn't match up to reality. Then it seems like we have suddenly caused things to go wrong but in reality its just life and the only thing that had changed was our expectation. Next time try to focus on your own energy and have confidence and positive thinking in your own terms rather than things that are outside of yourself.
If I were to cast a spell to help me at a job or a task one might expect things to suddenly start going right and simply fall into place. This isn't always so. I may have more problems than ever but the spell is still working. Instead of expecting life to be easier expect yourself to rise to those challenges and be greater than you ever thought you could be. That is the true magic.