I've had little self confidence for as long as I can remember and it's painful.

Going to job interviews and thinking I have nothing good to say about myself and no achievements, not being able to talk to people because of being so anxious about their opinion of me and sometimes going as far as purposely failing things or obviously making a fool of myself so that no one will really know what I can do when I put an effort into something because I don't think it's good enough.

But that's just my experience, everyone has different levels of confidence and different experiences. 

Having confidence is not a thing that can just be achieved, gaining confidence takes time.

One way that has helped me to gain confidence is to write a list of all the good events that have happened in my lifetime, so that when I'm not feeling my best I can look back and remember that not everything is all that bad.

Again, everyone is different and has different experiences. If your self confidence is getting you down, talk to somebody about it who can help, after you find your right method your confidence will be up in no time!