Zale Tabakman asked a LinkedIn question on Self confidence. Here's what I think:

To me, self-confidence is all about sincere, full and unconditional acceptance of who you are and how you could provide value to the people around you.

During some of the lowest points in my life, self-confidence is the only thing that got me going.
Another thing I observed about self-confidence is that it is contagious. Confident people give out an aura of confidence to the people they work with.

More on this at Zale's website.