"Well, it is frustrating, but most of us understand and support the fact that everything needs to be right," said astronaut Leroy Chiao, who has flown four missions in space four times, including a six-month stay on the International Space Station. "The crew would have had a rest, then another big push to be at the same level of preparation."
Shuttle commanders and their co-pilots will spend time in specially-modified jets NASA has for them to practice landings. If astronauts have been assigned spacewalks, they will spend time in the Neutral Buoyancy Lab, the giant swimming pool in Houston that has turned out to be the best place to practice working in weightlessness.
"The trainers are great. They'll find things for us to do," said John Herrington, who performed three spacewalks on a flight of the space shuttle Endeavour.
Different astronauts handle the emotional roller coaster of a delay differently. John Grunsfeld, a veteran of five flights, said he learned to urge junior crewmates to learn how to "manage frustration." Herrington told ABC News it was fun to hang out at the crew quarters in Florida: "It's kinda fun. They feed us like royalty."
Mike Massimino, who came within two weeks of launch on his second flight -- and then was faced with a six-month delay -- said he learned to be philosophical: "Better that they find the problem while you're still on the ground."
Some astronauts will tell you the truly special moment is not liftoff but "MECO" -- short for Main Engine Cut Off -- the moment, eight minutes into the flight, when the engines shut down and the crew, finally in orbit, enjoys the first sensation of weightlessness.
So perhaps the prize for equanimity in difficult circumstances goes to astronaut Steven Hawley, who was a crew member on Discovery's very first flight in 1984. The countdown actually got to its final seconds, when the main engines ignite and build up thrust. But then, with just four seconds to liftoff, the rockets dangerously shut down before the shuttle had moved an inch.
Hawley broke the tension: "Gee, I thought we'd be a lot higher."