CNBC's Jim Cramer told investors it's important to use big rallies to prepare for the down days.
In other words, you should raise some cash when your stocks are on a roll.
"The next time we get a big up day or two, please, I'm begging you, use the strength to raise some cash," he said.
"You might not know it, but without cash, your portfolio has zero flexibility, and the best time to raise cash is when the market is on fire."
But this does not mean investors should sell everything during a rally, Cramer said.
Persons:
CNBC's Jim Cramer, Cramer