Firstly, I haven't found anything that is 100% effective on every crisis. Sometimes a thing helps and sometimes it makes me worse, these things always change from person to person and crisis to crisis. I just listed what generally works for me and may help someone that deals with anxiety too.

• Listening to relaxing music: I use meditation songs, background noises or just instrumental songs (especially piano) to calm myself down.
• Analyzing the situation and telling myself I'm safe: when I start to feel anxious out of nowhere, something that helps me is analysing everything thats happening around me, what I'm doing and what I'm going to do for the rest of the day until I clearly realize that nothing bad is going to happen, so I keep repeatedly reminding myself that I'm safe and things are fine.
• Writing down my thoughts and organizing them: When I'm about to face a situation that can lead to a lot of possibilities or when I'm going to have a lot of busy days, I like to write a mental map of my future routine, everything that could happen to me or just generally organize my thoughts. When they're all mixed on my head things seem much worse and scary than they actually are.
• Being really gentle with myself: In these days I try the hardest I can to treat myself the way I would treat any of my friends if they were going through somehing bad. Sometimes I even use cheesy nicknames with myself (its really cringy and embarrassing but it's also really comforting so its ok)
• Controlling my breath: Breathing not necessarily deep but really slow almost always helps me to calm down.
• Trying to focus on the part of my body that's tense and relaxing it: If my stomach, shoulders or any part of my body starts to contract because of anxiety and it's still light, I try to relax that part and don't get all tense.
• Focusing my attention on external things: When my body starts to feel the anxiety symptoms and I can't control them, I try to focus myself on any external thing. It can be some show or fanfic or just count everything green that exists in the place I am.
• Distracting myself the entire day: There are days in which I wake up and I can feel that I'm going to be anxious the whole day, so if there's nothing I have to do on that day, I try to distract myself the whole day on something comfortable like binge watching something I like.
• Trying to be with someone i like: I hate being physically alone when I'm anxious, so I try to spend the day with a friend or one of my parents. Something that I usually do is try to watch some movie with my mom.
• Taking a hot bath: The hot water relaxes my body and I feel much better when I'm clean. When I'm anxious because of something on social media or something like that, the time I'm forced to spend alone in the bath helps me a little too.
• Colouring: I love colouring and it always makes me relaxed. When i'm not home or not in the mood to colour with real colored pencils and things like that, I just use some of these apps that gives you a black and white drawing and you colour it.

And when it's really bad and nothing helps:

• Staying still: when my anxiety is really strong, the only thing that helps me is laying on my bed under heavy blankets and trying to move the least I can. It gives me some spasm but eventually I'll fall asleep or just calm down a bit.
• Crying if I have to cry: my body gets really exhausted after crying during a crisis but its better for me than holding it. Again, I get so tired I eventually end up falling asleep.
• Just accepting it and hoping that i'm going to be better the next day.