Set small goals. My first goal is to say 2 sentences to a girl/guy. Do that, then you will see how well that goes. You basically can’t fail, so that will engender more trying. Then when that gets easy, raise the bar.
Long story short, people think that the worse case scenarios are WAY worse than they are. So when you start to actually do it and see that things start going well, you’ll want to do more. Success breeds success.