In my opinion, breathing is the most important key. Breathe at a steady pace. In through your nose and out through your mouth.
Listen to music. Even if its not your interest, you've got to have at least one favorite song. If not, listen to classical music. It's very calming.
Find a comfortable place for you. Maybe it's the couch in your living room or your new bed in your room. Just be comfortable.
Keep warm. You can get stomach aches when your hand or feet are cold so stay toasty in a blanket or put on some layers.
Take a walk outside. Get some fresh air and some time to think just by yourself. Solve out your problems or just let your mind wander.
When I'm stressed or have an anxiety attack, I like to make a song or a rhyme.
Find things that make you comfortable!
The creator of this guide has not included tools