Does Negative Thought Lead To Bad Things Happening?

You see, every time something extremely good is about to happen to me or people close to me, I try so hard not to think about it, reason being that so many times I feel like my positive / negative thoughts influence its outcome.

Once I had a contract, budget approved, etc, I had started making plans on how to invest the profit, I thought so hard about this contract. To my greatest surprise, client cancelled. This one was particularly strange, because my client was very excited and almost wanted us to deliver like yesterday, but one day, from no where, Oga said we shouldn't bother anymore.

So Here I am, thinking and researching deep about how powerful our thoughts are and if Good/bad thoughts can change the outcome of an event.

Is it possible to think negative/positive thoughts that would start manifesting? 

last to comment may get a shopping voucher from Nanm