Self confidence or lack thereof

Self confidence... What is it? How does one get it? Are we born with it or do we develop it?
I am a lifetime self critic. I like to say I can do anything but deep down i lack true, real confidence. Self confidence. Others have confidence in me, they see my potential and tell me they see it. But I don't. Why? Is it because I do not want to be selfish by having too much confidence in myself? Maybe that's it. I love giving and helping people, so why would I be selfish in my confidence when I can help other people have confidence in themselves? Or am I scared that self confidence will turn into self pride? What is the difference? 
So to my friends and acquaintances out there, I fully intend to have more confidence in myself, starting NOW! I CAN do anything. 
Phil. 4:13 I can do all things through Christ who gives me strength