He was having a very bad day. Very bad days earned the qualifier if any of these three things were happening:
1. The Earth was being destroyed.
2. Arthur's life was in danger.
3. Ford Prefect was in the vicinity.
The first had happened often enough that Arthur had grown used to it. The second happened with such startling frequency that Arthur was considering changing it to something else (being wrongfully accused of murder, for example).
The third, however, was most definitely the reason for every very bad day Arthur had had since the first time the Earth had been destroyed.
To wit: Ford and Arthur were standing in front of a cash point machine, trying to withdraw some Altarian dollars. The cash point machine wasn't having a very good day either, and decided to make its bad mood known... by not returning Ford's Din-o-Charge card.
"Look here, Mister Prefect," the cash point machine said in a school-marmish voice (Arthur wondered if the Babel Fish did accents as well as translations). "This card is expired."
Ford frowned. "What do you mean, expired?"
"This card is no longer viable for any transactions," the cash point replied.
"It was rhetorical," Ford mumbled. "When did it expire?"
"Two million, six hundred seventy thousand, five hundred thirty-two years ago, last month," the machine replied, and spit out the card. "SFR Enterprises thanks you for your business."
Ford kicked the machine for good measure and sat down, sighing. "Well, that's that," he murmured.
"That's that?" Arthur exclaimed. "We need to be on that shit...that ship! The ship! We need to be on it!"
Ford shrugged, leaning back on his elbows. "Let's be cool."
"I have NEVER been cool in my entire life, Ford," Arthur replied, sitting down next to him. "What are we going to do?"
"We have a few options," Ford said. "You won't like any of them."
"Now you're starting to get to know me," Arthur said, sighing. "It only took you two million years."
"We can sell your blood."
"I said you wouldn't like it."
"You said we had a few options?"
Ford coughed politely. "Well, uh. You're technically the last human in the entire universe. At least...this universe."
Arthur frowned in thought, and then sprang up as if he had been bitten. "ABSOLUTELY NOT."
"Blood it is, then!" Ford said, popping up. "Let's go! We have a shit to catch."