There are dividends, which is money you get before selling.
And there are tricks one can use to get money without selling. Buy, borrow, die strategy allows you to borrow on what you own(which is not a taxable profit), payback the borrowed money(which is a tax deduction loss), and hold everything until you die(when the capital gain asset values will be reset to the current value). If done correctly, you can have plenty of spending money, and never pay a penny of taxes.
Usually, you want to try to live off someplace between 2% and 4% of your earning assets. Dividends are in the 1% to 2% lately, but would probably go up if there was a stock market crash. So you will be selling a few percent of your stocks a year to makeup the shortfall.
When you reallocate the stocks and bonds mix, you would also either buy or sell stocks. The cool part about that is you will tend to sell stocks when they are too high, and buy stocks when they are too low. While on average you might lose somewhere between 1% and 2% yield due to keeping 10% in bonds, you will add between 2% and 3% average yield by selling high, and buying low. The 10% bonds actually means you make no just more stable returns, but also better returns.
You might be forced to sell some of the stocks when everyone else is selling, but not much. You are selling on average one or two percent a year, but when the stock market is down, you are most likely selling bonds and buying stocks. You are taking your living expenses out of the bonds part of the portfolio.
If possible, you want to reduce your living expenses during the down times. That is often easier said than done. But this strategy should carry you through even if you cannot reduce your living expenses much.
Timing the market is hard, and I do not want to even try with most of my retirement funds. So I am forced to just ride the market down and then up like a roller coaster.
I did take a tiny bit out (5%) and try to predict/time the market. That has already made me enough profits to more than replenish the 5% and makeup for the market losses. I am ahead of where I wanted to be.