Freak out for approximately 10 minutes. More if you don’t have backups or haven’t saved your work recently.
Try turning your computer off and on.
Not working? Try again.
Do you know anything else to do?
No? Ok, try again.
THAT’S NOT WORKING.
Start trying to slow your breathing down.
Figure out your entire life. Consider that maybe you don’t need a computer, since you have a smart phone. And hey, maybe you don’t even need that.
Think about how nice it would be to just write and not have to deal with technology at all. Maybe you could even become a hermit who lives in the woods and sends in beautiful, finished manuscripts to publishers who love you, your work, and your eccentricity.
Give up on this dream and take your computer in to get it fixed.
Sit there worrying and biting your nails while the computer fix-it person fixes your computer.
If/when everything works out okay and you get all your files back with your computer running better than ever think about how amazing your life is sometimes. (If everything doesn’t work out perfectly, feel free to curse a bit under your breath and cry over lost work and then move on to step 10)
Triple backup all of your files for the rest of your life, including hard copies. But also, think about the impermanence of life and how much all of it can matter and then not matter at all in an instant. Think how beautiful, tragic and important it all is.