I've always kept my anxiety in check using a lot of "logic." It's "just" anxiety and I've dealt with it before and will have it again. Getting myself in a position so I'm very aware of my physical surroundings, am out of my "head" and more in my body helps me. Talking to someone else, going shopping/being around other people, or working on a very detailed task can be a good help to me. Check in with all senses (feel corduroy, tree trunks, etc.; make a cup of tea or hot chocolate, bake something and smell the smells; watch something concrete and literal -- cats/children/dogs playing, birds in the yard, cars/traffic in the street; listen for "unusual" (to you) sounds -- specific birds (I'm on the water, have seagulls :-) or just the sound of the washing machine, drier, dish washer). The more you can combine things in literal, everyday ways, become "mindful" the more grounded you can feel and the less influence your anxious feelings will have over you.

Usually we're afraid of things in the future or which are in a sense, "imaginary"/not real. Shifting focus to the real/concrete helps me relax some. When I relax (like waking up from a bad dream) I then only gradually go back into my "head" by working hard on an intellectual exercise (my schoolwork :-) like reading a nonfiction book or doing physical chores. If it's the middle of the night, I sometimes get up and eat some yogurt or cottage cheese or other healthy comfort food (cream of wheat/oatmeal) and do a few exercises/stretches and decide to treat the "problem" as if it's a bad dream I am going to have so decide to go to sleep and have it and make the best of it in the morning.