You want a valve that doesn’t leak and you try everything possible to develop one. But the real world provides you with a leaky valve. You have to determine how much leaking you can tolerate.
-Arthur Rudolph
Bonus trivia: Rudolph was a notorious figure because he designed the V-2 rocket production facility, which used Nazi concentration camp labor. He was captured by US forces and brought back, eventually joining the team that designed NASA’s Saturn V rocket.