However you frame it, there's always a time you start withdrawals. And if when you planned to do that coincides with a dip, of course you'll have second thoughts.
Did so about a year ago based on SMAs and momentum. Only wish there was a cash option to put have them move everything to for the time being, but only had bonds as an option.
Best thing is to watch out for the SMA support levels. Just got through a major death cross and looks to be heading further down
Though you should have options. Don't retire in a down year. Start moving things to safer investments several years before you retire. Don't spend as much that first year. Still the numbers given are good examples and something to keep in mind.