This video says to visualize a place that's beautiful, safe, and peaceful when you feel anxiety.
He said it shuts down the fear/anxiety. So I tried it when I was going to ask a girl out a couple of
days ago. I started freaking out a little bit so I visualized my safe place. I think it worked. It made
me think about my safe place and forget all about the fear. My safe place is a beach on another world where there's no living creature other than me. You can make up whatever you want.

https://www.youtube.com/watch?v=KYJdekjiAog

There's some other anti anxiety videos on youtube but I haven't looked into them.

Oh here's another thing I did before which I thought of myself. I was really scared to ask out a girl one time, so I repeated to myself, "I'm confident and happy" over and over until I was ready to go ask her out. It worked.