Alright first my experience.
I used to work in a really stressfull job, IT helpdesk. About a year into working this job I broke up with my long term girlfriend, moved out of the flat we were living in together and started living with my brother. I hated living with him, the combination of these factors made my life very stressfull.
One day at work I had a really bad migraine. At first i didnt know what was happening as my vision went blurred and I was really out of it. This was a really bad experience and I started getting really scared I would get another one. I was really aware of how I felt all the time as I was constantly monitoring myself for signs I was going to have another migraine.
This constant fear of having a migraine escalated into a fear that there was something seriously wrong with me. One day on my way to work I got this strange feeling and I was convinced I was dying and needed to go to hospital, that was my first panic attack.
I was diagnosed with a panic attack disorder by my gp, for a period of time I was too scared to leave the home out of fear of having a panic attack. I was under extreme stress and was on medication. During this time I was constantly scared of having a heart attack, some strange things like going blind, but a big one was going insane.
Thats when I first experienced depersonalization/derealization. It was a scary experience. Just now can I say that I feel I have beaten it.

For starters, drugs are not going to fix it. There is a concious process you must go through to fix this.
You can and will get over it. most of the distress is caused by fear of what is going to happen or what this will expand into it, its not the actual moment you are in. Eventually you get used to waiting out the experience, so much so you have no fear of it anymore. eg I used to get the depersonalization problem in public, I would be scared I was going to nut out or do something bad because of it, the event I feared never came.
Once the fear is gone the problem is gone, its like an illusion of sorts.
It is very important to NOT to avoid ANY situations which you fear will bring this on. Dont give it an inch, if you know anything about operant conditioning you will understand the conseqeunces of avoidant behaviour (including the positive consequences of not avoiding a situation).

Its actually a state brought on by a normal functioning brain. The state is found when you are examining your self/thoughts for something to be scared of due to paranoia or stress. People can be very creative when they are paranoid, this is a perfect example. Most thoughts and ideas found when in this state of paranoia can be quickly rationalized so you disregard them as a threat. The state of Derealization & Depersonalization is unique, once found you attach all these negative possibilitys and any other scary creative ideas your paranoia creates.

I'll stop now to limit the size of this post,
Ask me any questions if interested