I think that whatever the future holds, making your nest egg as big as you can, being ABLE to live frugally, and always being able to make an income should take away whatever worries you can imagine. Apart from global thermonuclear warfare, if you have have a job that you love, that you might would do for free but actually provides you income, you should be ok. You may not live as extreme as some on this board, but if you can discipline your life to live frugally IF YOU NEED TO, then you should be able to weather even very tough market environments. Having a repeat of the '70s would be very tough if you are trying to live off stock investments in a down market with high inflation. But being able to live frugally through that, along with making a little extra income on the side, should allow you to not tap into your investments if they are down.
Personally, if I had no side income besides investments, and I was to FIRE in my 30s, I'd want at least a $2 million nest egg in today's money. This way if there was a sustained bear market I could weather it without taking too much out. But that's just me.