Is this self-doubting that is causing my indecisiveness?

I usually like making decisions. It feels good! But when I am countered such as now I have a second thought.
I was in the midst of taking on another great business opportunity but have been feeling uneasy about it. A business opportunity came to me then I got overwhelmed with a few other opportunities that I had decided to go with as well. When I feel good, I am in full confidence to handle them all, however when I doubt myself for the ability to succeed, I start thinking and looking for reasons to fail. And I start justifying my decision to withdraw fair and reasonable to feel right until I am reminded of how great the opportunity is. This leads me to not being able to make decisions because the decision might be based on my fear and I regret it later.

How can I trust myself that I can do this without ever doubting myself at all?