In 1962 Bob Dylan gave the worst possible advice to bridge players when he hit the charts with "Don't Think Twice." Nonsense. We've got to think at LEAST twice... maybe more than thrice.
Did you know that the number of decisions in a hand of bridge rivals the number in a chess game? Not only do we have multiple decisions, we've got the vagaries of a Pard to deal with. Which is the best and only sometimes the worst thing about bridge.
But I digress. Let's look at some situations where we need to think twice. Pard makes a Takeout Double and we need to respond. We need to show two aspects of our hand... shape and point count. Remember Pard is a) short in their suit, b) probably has four in any unbid major, c) has an opening-ish hand, and d) can tolerate any suit we bid.