Your self-confidence is your sense of self. It is your belief in your capabilities to perform at the required level, attain goals, learn new skills and achieve your objectives. It is the most important psychological contributor to performance in the business world because even if have all of the ability in the world to accomplish a goal, if you lack confidence in your abilities, you won't use them to their fullest extent to pursue success.
Self-talk drives self-esteem which drives self-confidence. Everybody, and I mean everybody, faces self-doubt. People with higher self-confidence and ability to manage personal self-doubt develop higher self-confidence. Fortunately, confidence is a skill that can be progressively developed with awareness and practice.
Comfort zones are boundaries are designed by us for personal safety and comfort. Most people have difficulty leaving their comfort zones or even widening it. Unless you are an accomplished business person (usually experienced), it is highly unlikely that you will succeed without stretching and leaving your comfort zone. People unwilling to leave their comfort zones are generally less adaptable and do not have a growth mindset.