Does deleting a cookie from your web browser also invalidate it/the session?

I think this is somewhat privacy related, so I decided to ask. I'm paranoid about XSS software attacks, so, I decided "Why not just delete my cookies?". I don't think I thought that through fully and didn't check if that also completely gets rid of them.

So, does deleting cookies stop XSS attacks or invalidate your login sessions?

For example, say I delete all my cookies from chrome or firefox. Are they gone permanently (no one can use them to …

browser privacy session web web browser