Why are airplanes described as the safest method of transportation? I will have my first flight tomorrow. It is my first time that I get into an airplane, and by the time am  writing this post, I am feeling anxious and stressed a lot. I even don't talk to anyone as it is the last day of my life and need to live it alone. I read that this is called "fear of flight" or "phobia of airplanes".

I read online on all related sites, that the airplanes are the safest transportation mode. I could die with a car accident while I am getting to airport 20 times more than be killed in an airplane crash.

All sites said that I should understand more about airplanes, and that would release the tension and make me better.

I am thinking to cancel the flight and the 330$ will go through the wind as we say in my country, and not be refunded. I read a lot of things but all are technical, and I didn't understand any single word, especially that I am a person that don't have any mechanical or technical background to understand it.

My doctor told me to start taking "Xanax" and that would help me be fine on my less than 2 hours flight (most of it is over the sea that's why I am more anxious).

Why are airplanes the safest method of transportation? Why aren't ships the safest? Because in 3 years I didn't hear of an airplane that sank.
Good news

The good news is: you really are safe in an airliner, so safe that you could spend every minute of every day of the the rest of your life flying in one, and still not face any greater meaningful risk of a disaster.

It's difficult to answer your question why it's so safe (i.e. what makes it safe), but the record is there, plainly, that it is so safe.

Bad news

The bad news is: if one has an irrational fear of flying, then no objective facts or understanding will help lessen it.

If the fear is based on misunderstanding or lack of knowledge, then of course learning more will help overcome it. However, that's not the basis of a phobia, or the kind of fear you seem to be describing.

Advice to understand flight and aircraft is well-meaning, but not actually that useful. Someone can have an excellent understanding of aviation 
engineering and aerodynamics and all manner of subjects, and know that it is exceptionally safe, and still suffer from crippling fear of actually flying.

Everyone is different, but such fear is often brought on by an event or change in life that has nothing whatsoever to do with flying, but somehow gets expressed in a fear of flying.

The comfort and support of another person on board could be the most valuable thing you seek before your flight. I'd suggest expressing your fear, without embarrassment or shame, to the staff at the gate. They and the crew on board will have helped people in such cases many times before, and they are good at it.

Simply getting used to an object of fear is one of the best ways of dealing with it.

I hope you make your flight, and I hope to hear that having done it once, the fear diminished by being stared down, and that subsequent flights render it lesser still. Please tell us about it here.