I don't really know how to help you overcome your fear but I know a good trick that can help you overcome your lack of self esteem
You will need a piece of paper and a pen!
Now take some time alone and write down all your achievements in life. From the minute you started walking until now. All the things that make you proud of yourself. Take a good thought about it and take your time. Make the biggest possible list that you can ever make. Write even your smallest achievements.
After you finish. READ them.
It will feel great.
NOw take this list and put it in a place that you can see it every day. And read it as often as you can and if you can add some more things on it then do so! And feel even more proud of yourself. This will help as a good ego boost. Day in and day out read it and feel how great you are. Think all the great things a great person like you deserves.
It is then that you will only realise that the only obstacle that you don't have them is the lack of effort to go and get them.
For insecurities:
Stand in front of a mirror. Write down all the things that annoy you. Also take some time and write down the things that annoy you and you cannot see in the mirror =P. Read them. See every point as a problem with a solution. Pick the easiest point in your list and start from there. Even if you don't cross everything in your list thinking about the solutions will make you feel good.
For fear:
Best thing that can help you with any sort of fear is NLP.
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Apart from these, as a girl I want to reassure you that we love when men approach us. Even if we say to our gfs that we get annoyed that soooo many men approach us we just love it. Even if we are taken. Even if we don't fancy the guys. We just so love much love it.
And you know what they say, you cannot win if you don't risk to fail!
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To understand more about self esteem check Maslow's pyramid.
