Psyching myself out from doing anything

Here's an example: On line waiting to get food at a ski resort's lunch place. Cute girl infront of me waiting. She looked back at me at one point but i did nothing but look away quickly. I just had this feeling come over me like "damn, why didnt I do anything" but then quickly thought "eh not worth it, what would talking to her even do"....

Highseddit, sometimes I get the feeling that talking to girls isn't worth it and that being introverted and keeping to myself is fine. I don't know why, because then I wish I had someone to hang out with or whatever. How can I get over this?