Sales gurus say it takes a strong dose of self-confidence to succeed in sales. While self-assurance is necessary, it may also send a message to customers that a salesperson is arrogant.
Source: Sales consultant John R. Graham
What's needed is a balance so we can clearly understand what's going on with customers. Doubt does that by keeping us sharp, alert, and always on our toes. How many times do we say, "I should really have picked up on that issue," or "I wish I had thought of that," or "What could I have done to improve the proposal?" That takes digging down and asking questions. It takes doubt.