HOW FAST IS TOO FAST

Thanks for taking my question. I'm 69 female, still working full time, and have lone AF for 4 years. My specialist here in OZ tells me to take a pill(Tambacor)and wait for my heart to 'settle' when I have an attack. I have had a stress echo which was normal, an ultra sound which was normal, I have good blood pressure 130/80, and an angiogram showed my arteries to be normal.Usually my heart is beating so fast I cant count because they are 'all over the place'  I get chest pain and jaw pain, am short of breath and get panicky.
Some triggers I have noticed are sleeping on my left side, eating too fast, alcahol (alcohol), getting stressed and overdoing caffiene.
I have a constant feeling of a lump in my chest/throat as if I'm going to go into AF at any time and I suffer GERD.
My questions are, how fast is too fast when I'm in AF, is it OK to lie down and go to sleep. Should I exercise?
Should I keep on at work. And the big one.."How do you learn to live with the constant fear you may die" this is a
nasty infliction and it must cause major stress to anyone who has it.
And finally, are there any new medications in the pipeworks, and have you heard of any studies using Magnesium as it does seem to help. And can it take Magnesium if my kidneys are below par.
Thanks Again

[Jerry_NJ]

Your description sounds more like permanent (chronic)  AFib (that's what I have) tha Lone AFib.  

Whatever the case, a HR at rest of over 100 bpm is generally considered too high and requires treatment, usually a beta blocker, I believe (true in my case 100 mg Metoprolol or more a day).   With permanent AFib and a strong dose of beta blocker I don't think I'm going to die, well not anytime soon and from the AFib.  My HR runs in the 80s usually at rest and it jumps around, some periods are in the neighborhood of 100 and some are closer to 80.  If I increase my BB to 200 mg I even get some HR in the upper 70s.  

Not sure any of this helps, and I can walk but not run, i.e., your question about exercise.  I have to take hills slowly, even stop  to rest if on a trail on a hill side, too steep for a road, but not a cliff.  I was a running up to the age of 67, but when I lost sinus rhythm at about 67.5 years old I stopped running - I remain in AFib and don't run, but as I said, I do walk.  I am retired but very active.  The BB makes me more lethargic, or maybe it is being 70, but I still mow, garden, paint the outside of a two story house, and walk can walk a couple of miles (at a slow 3.5 or so miles per hour) without any trouble, if the ground is mostly level.  

[AMJOY]

Hi Jerry

Thanks for the response. My attacks are usually spaced by a month up to 3 months altho the last few times have been fairly close together. I think because I have been run down and overworking.
Hopefully in the future someone will find a a cure for this as just googling  different sites on the net shows how many people suffer and are fearful of it.
I try to not worry too much...and have found that just lying flat on the floor and deep  breathing with some really good music with a powerful slow beat is helpful.