Meditations
I heard on an "Overcoming Anxiety and Fear" course by the mental health charity MIND that the more regularly you do meditations (breathing ones and muscle relaxation ones etc) the easier is to relax yourself when you find yourself in a state of anxiety/stress.The course facilitator also said if you get good at focusing on your breathe and being present, you can use it as an anchor when getting anxious.
When I first started doing meditations I was hopeless, couldn't concentrate at all. However, I do feel the more I have done them the easier they've got. I've struggled a lot with anxiety on my journey, and I often find myself feeling calmer when I've been in state after a meditation as well. Nowadays, I find they are helpful for my anxiety, rumination and any paranoia I may be experiencing.
Below are a few examples of meditations that I personally like - but there are many out there. I know some people may have a preference on the gender or nationality of their guided meditation guides.