Beliefs about Cancer

I’ve been practicing thought ladders and new beliefs, but my question is, is it possible to form a new belief even if it is on something that is out of my control? I am a new cancer survivor and I have an unnecessary belief that my cancer will come back. Though this is a realistic possibility, I am not benefiting from believing this. I want to live as if I believe it will not come back, but that is difficult because I can’t know that for a fact.