How do you cope with anxiety and fear?

I’m only two weeks out from my first treatment for stage 4 adenocarcinoma (chemo and immunotherapy) and this past week has been quite an emotional roller coaster. I had unbearable anxiety the past few days. I’m still early in all this and I know I haven’t fully come to terms with my diagnosis or processed all the existential stuff that goes with it.

How do you cope with the fears, and manage the anxiety?