A truck a day.

The second half of this sentence is "happy as a fairy".

"A car a day is as happy as a fairy", which is a joke and is usually used to describe a relaxed and happy lifestyle. "One truck a day" refers to transporting goods every day, which may be the need of carrying goods at work or dealing with some trivial matters in life; And "happy as a fairy" means that this lifestyle is very relaxed and happy, which makes people feel satisfied and happy.

It is an exaggeration to say that "a car a day is as happy as a fairy". Not everyone can spend every day easily and happily. By arranging time and tasks reasonably and maintaining a positive and optimistic attitude, everyone can make their life more substantial and meaningful.