Reasons behind the issue raised by you might environment around you or some incident which might have created some sort of fear in your mind. You need to introspect the incidents occurred around during last few years. Another reason might be your excessive emotional involvement in something. Do anaylise the things and find out the reason for yourself feeling weak. It might be possible that you are in touch of some people who are emotionally weak or depressed. Please revisit your social circle and events and then come up with the points you notice so that we can discuss further. In the meantime don’t allow the weak emotions to overpower you and for that you can read some good stuff on internet and watch motivational videos.