It means take the money that's being offered instead of hoping for a higher valuation and less dilution later. Keep spending low and cash balances high. The leading cause of failure among startups is death. This is Johnson's Corollary to Kleiner's Law of Appetizers. It's named after Craig Johnson, the founder of Venture Law Group.
Few companies fail when they still have money in the bank.
Live to fight another day or until the world recognizes your market. Ask for less than you need. In any business except high technology, you should ask for more money than you need. However, the opposite is true in this market.