You should take a break from everything for a while and think about your strengths and weaknesses. Ask yourself if you are making the most of your strengths. As for the weaknesses, the mere fact that you have acknowledged their existence is the first step towards overcoming them. Ask yourself if these weaknesses are having a significant impact on your life. If they are, then you should start thinking about ways to curb them.
Analyse yourself honestly to discover whether there is a particular person or experience that has shattered your confidence, or if your lack of confidence has resulted from a series of incidents and experiences over the course of time.
Surrounding yourself with positive people will help you feel more confident. If there are certain people that make you feel nervous and less confident, it is best to avoid those people for the time being, and spend more time with people who make you feel at ease, respected, and in demand.
If there is a particular activity that you are constantly failing at, and which is consequently hurting your confidence, take a break from that activity to regain your lost confidence. Get back to it only after you have prepared yourself properly for it.
Utilise your free time to do volunteer work. Doing something for the society will help you feel good about yourself and make you feel both wanted and useful. You will find yourself getting far more than what you give to others.
Talk to someone who has served as an inspiration for you in the past. They may have experienced what you are experiencing at the moment. Seeking their advice may help you to hold your own while going through a difficult time, and help you bounce back with renewed confidence.
Set realistic, short-term goals. By completing these goals, you will begin to feel more confident and eventually get to a point when you can start pursuing more challenging goals.