as others have said your chances of being involved in an accident on a plane are astronomically small. So small that my chances of being struck by lightning as i type this are pretty good- even better- being a big lottery winner. It's true.
But did you know that the survival rate for those involved in plane mishaps is around 95%? Here's what i do. I always make sure my seat is no more than 5 rows from an exit because those people will usually be able to get out if there's an accident. I then imagine myself with my eyes closed making my way to the exit in a calm and purposeful manner just so i have that in my mind in case i need it. Check for the in floor and other lighting around the cabin just so you know it's there.
After that i relax and listen to the safety briefing using the card while noticing how many others don't bother or are already asleep or on their phones. Other than being alert to my surroundings during takeoff, landing, and keeping my belt on at all times, i've done all i can do to keep myself safe so i can enjoy the flight.
Having said all that, accidents do happen. I've been in three. One was an on ground collision with a truck which punctured a fuel tank in the wing. Another was a case of wake turbulence from a too-near 747 where we got pretty badly bounced around. Only those without belts were injured. Remember that the plane can take way more punishment than you or i can without ill effects.
Finally, i was on a plane that slid off the end of the runway (at high speed) that was slush and ice covered. Other than a long delay we were all fine which is more than i can say about the plane's landing gear that collapsed.
So i guess what i really want to say is that flying is really, really, safe and even if you are involved in any kind of accident your chances of coming through it are really good, too.
As someone with my own "irrational" fears i know this won't change your feelings buy you never know?