I look at it this way Orwell. How often does the market actually fall 40-5o% Not that often . But I agree you need to be prepared if you think that it could and adjust your strategy to some degree.
As far as holding stocks through downturns well obviously there is a time to sell most stocks ,no matter how good they are , but there are some stocks that I'm just not interested in selling whatever the market conditions ,that to me could be an opportunity to buy more . I've always believed in staying invested to some degree and that's stood me in good stead over the years . I'm not pig headed enough to think that that may not turn out well on the rare occasion but overall that's my style. There are always stocks that do well and opportunities whatever the market.
Obviously in a long term bear with a significant grind down you don't want to be holding a lot of stocks . It's a wealth destroyer to be fully invested under those conditions.
From reading your posts it's evident that you're becoming more convinced of that as a strong possibility with each passing week