Bump it up up up, bump it up up up, bump it up up up, I'm in Fireeeee~
If you ever suffer from an anxiety attack, are panicking, generally need something to help you calm down, I would like to highly recommend
Breathing App, a minimalistic app that will help you guide your breathing with a simple visual cue or sound if you want to close your eyes. You can change the time of the session, and the in-out ratio of the breathing (the longer the out exhale, the more it will slow your heart rate and thus calm you, but too long exhales might be uncomfortable or you might simply not wish to become sleepy. 5:5 and 6:6 depending on what you're comfortable should stabilize your heart rate).
Then there's
Calm Harm, which has helped me take the edge of many a panic attack. Originally created to help people with self harm, I find it can work wonders with pretty much any overwhelming negative emotional state. There's several categories you can choose from: comfort (self-care), distraction (list as many songs as possible as you can that start with [random letter]), expression (try to express what you're feeling through writing or art, then tear it up), release (sing along with something at the top of your lungs), and breathing exercises (what it says on the tin).
These are just a few examples, because the list of suggestions in each category is
very long. However, you have the possibility to hide suggestions if they're not your thing (for example, there's a handful that involve prayer and the like, but if you're not religious, you can just hide those).
This is an app that I suggest to pretty much anyone who mentions having anxiety or something similar, because it's personally helped me so much.
Oh, and obviously both these apps are free and work on both iOS and Android.
