Self doubt

I have doubts now and then.
I sometimes doubt that I could make something work as I get deeper into the domain.
I sometimes doubt myself about whether or not I could success.
I sometimes doubt myself about whether or not what I am doing will turn out to be successful.
I doubt myself everyday.

But that's natural. I think these doubts are just a signal that makes you be cautious. Cautious about the decisions you're about to make.

Be doubtful, but also confident.