I'm not a very self confident person. This is used as self assurance in one's judgement, ability and power.
I'm just the opposite and sometimes it gets me into trouble! I should learn when to keep my mouth shut, for example.
People increase self confidence from experiences of having mastered many different activities
That's a very good way of gaining confidence. Have you tried many things to find something you enjoy and are good at?
Not really. I need to though. It will increase my feelings that in the future I will be able to accomplish what I wish to do. 
You just have to believe in yourself. Start with small things and build up. Before you know it you'll be an expert in whatever you choose to learn.
task” and therefore is the term that more accurately refers to specific self-confidence. Psychologists have long noted that a person can possess self-confidence that he or she can complete a specific task (self-efficacy) (e.g. cook a good meal or write a good novel) even though they may lack general self-confidence, or conversely be self-confident though they lack the self-efficacy to achieve a particular task (e.g. write a novel). These two types of self-confidence are, however
Self-confidence
The concept of self-confidence is commonly used as self-assurance in one's personal judgment, ability, power, etc. One's self confidence increases from experiences of having mastered particular activities. It is a positive belief that in the future one can generally accomplish what one wishes to do. Self-confidence is not the same as self-esteem, which is an evaluation of one's own worth, whereas self-confidence is more specifically trust in one's ability to achieve some goal,