One issue is that we anchor on dollars as our points system to track whether we are doing the right things or not.
Our brokerage account values are quoted in dollars, our "net worth" is in dollars, our salaries are in dollars, and we think about retirement as a requirement for dollars at various times. This is a very lower/middle class way of thinking, rooted more in paycheck-to-paycheck culture than an entrepreneurship mindset.
We should be thinking in terms of the earnings streams we are buying. It is earnings that will support the asset's price in the future. Earnings will pay for buybacks and dividends. To retire, we need assets that will deliver decades of earnings, not a safety fund that might last 2 years. We seek to trade dollars for businesses that will earn profits for us in the distant future, not hoard or protect dollars.
When we try to hoard or protect dollars, we end up in "defensive" investments with no real return or we end up doing value destroying trades. Examples of value destroying trades include buying high and selling low, which destroys cash, or selling low and buying high, which destroys shares. Either move is a loss, accounted for in different units!
The alternative mindset is something like,
I want to reach a "FIRE number" of 3,600 shares of SPY, because SPY represents about $14 in earnings growing at 6-7% per year, and I expect to make sustainable regular exchanges from this position to dollars to cover my $50k spend rate during retirement, after adjustment for inflation.
or...
I want to own and operate rental properties generating $50k a year in NOPAT to cover my $50k spend rate during retirement, after adjustment for inflation.
or...
I want to own an REIT and preferred shares portfolio with a real yield of 5% to cover my...
or, even better, own portions of all the above with a plan for each to cover a percentage of the spending needs.
When the exchange rate between dollars and stocks fluctuates, we don't necessarily have to care any more than when the exchange rate between yen and euros fluctuates. It does not really change our odds of successful retirement unless we engage in value destroying trades. If our assets are currently selling for 5% less than what we paid for them, we did not "lose" $50,000 unless we convert all our shares back to cash. We still have the same earnings streams we originally bought - the shares. Did you know the US dollars in your checking account and brokerage depreciated 10% against the Swedish krona in the past 12 months? It seriously doesn't matter unless one trades on that emotion of loss.
In terms of whether or not our assets will support a steady stream of withdraws throughout a 40 year retirement, the month-to-month 10% swings are noise driven by analysts' ever-changing earnings estimates. Thus we should strive to accumulate shares, not dollars.