Nobody likes a jackass
Confidence is crucial. If you don’t believe in yourself, your organization, your product, and your prospect, then your prospect won’t believe in you. The confidence that you emanate will help your clients be confident in their decision to choose you.
People that lack confidence tend to overcompensate by being pushy and a jackass. And, just in case you didn’t already know this, nobody likes a jackass.
One Moore Thing: The only way to have real confidence is to have knowledge: knowledge of your product, knowledge of your client, and (most importantly) knowledge of yourself.