What is the best way to prevent a panic attack if you know you're going to have one?

Neural pathways...they're why we remember how to walk, talk and do stuff. They're also kinda responsible for one panic attack easily turning into months or years of the things. (Your brain remembers what happened last time and just goes down the same road). And the trick to cutting your attacks short is knowing that! So, if you're sitting down when it starts to come on, stand up. Or vice versa. Then say to yourself; 'I'm having a panic attack, this is just a panic attack'. Keep repeating that, just so your brain knows you're actually in control of this. Take some nice steady deep breaths; you need to regulate your breathing when this beast strikes; breathe in slowly to the count of 5 and out to the count of 5. Make them so you expand your gut as much as possible, if you look like you've eaten too much while breathing in, you're getting nice big breaths into you. Start to shake your hands out (keep repeating that mantra) or rub your temples (keep repeating that mantra) or take a few paces up and down, if you can manage it. Do something, anything to break up the normal pattern of an attack, which usually ends up with you on the floor, sweating profusely and struggling to get a breath. After a minute or so, depending on how long yours normally last, you should start to feel it receding. But if this is your first attempt at cutting them short, remember you're likely to still feel wrecked afterwards. Give yourself a few minutes to get your breath back or your body to get your adrenaline levels back into line. And if you want, you can maybe spend a another minute or so telling yourself that you just HAD a panic attack (past tense!). You're dealing with a very nasty physical and mental event but with a bit of awareness of what's happening you can start to regain control and even curtail them. Just by breaking the chain it's entirely possible for your attacks to become a thing that USED to happen to you. All the best, friend.