Volatility is a cost and an opportunity. High volatility means bigger moves, wider stops, and larger slippage; low volatility means quiet markets where breakouts fail. Realized volatility measures what happened; implied-volatility measures what options prices expect.
position-sizing should shrink as volatility rises so that dollar risk stays constant. atr is the usual tool.
Example: an asset with 16% annualized volatility moves about 1% on a typical day (16% divided by the square root of 252). At 48% volatility a typical day is 3%.
Related: atr, implied-volatility, position-sizing, bollinger-bands