Deeper thinking, exploration of more pros and cons, can lead to less feeling of confidence in a decision
The more arguments you come up with to support your decision, the less confident you will be that the decision is correct. Doesn’t that disturb you, as someone who prides yourself on thinking honestly, objectively and thoroughly about what positions to take? Yet the psychological paradox has been well researched, as described in Daniel Kahneman, Thinking, Fast and Slow (Farrar, Straus & Giroux 2011) in Chapter 12.
Our minds work harder and harder to come up with additional advantages of a course of action, and what Kahneman calls our System 1 brain, our quick and instinctive brain, misconstrues that effort as uncertainty and doubt. If the idea was felt hard to arrive at and formulate, the conclusion must be doubtful. That part of our mind does not weight and evaluate arguments; it fires off on ease and availability only.
This blogger has tried to come up with reasons for points made here, even going so far as to force and collect pros and cons (See my post of March 23, 2009: pros and cons of various practices, with 13 references and two metaposts.). Psychologically, and ironically, that effort may have instilled a sense of skepticism more than confidence! So think deeply about all sides of an issue but keep your neural eye open for the instinctive consequences, a feeling of lack of certainty.