Ok fair enough OP that's a hell of a lot more honest. Of course you are scared, we all are. Rather than making excuses it's way for more helpful for your own sanity to admit that.
Look this whole thing is terrifying, 2 years ago I had a stroke and I've never experienced fear like it. Any sign of stumbling anything , any fuzzy eyesight (although I know damn well I wouldn't get warning ) I panic. I really do.
However, unfortunately there are no real get outs in this, I'm sorry but there aren't. We could all isolate left right and centre....whilst of course it will slow it, ultimately there is absolutely no iron clad protection.
Only you can deal with this, and make it right in your head. Ultimately you have to decide whether to step up , do you think every doctor or nurse or paramedic is not scare when they go out to work at the moment ? Of course they are. But they know that the only option here is for everyone to work together and do their bit. Does that suck? Yes , does it feel unfair that some have to do it more than others ? Yes. However none saw this coming, noone is staying home to upset you , and no key worker is sending their child in to put you at risk. Everyone is trying to do their bit, basically you now need to decide of you will do yours.
Your employer is not calling you in for no reason. They cant claim the 80% if you are there, for the first time I honestly believe mostly everyone just wants to slow the damn thing and protect people. (Yes if course there are profiteers but ultimately it doesnt sound like there is reason yet to believe your employer is , you've misunderstood the 80 percent thing).