If those long days of sun, sand and sleep-ins are but a distant memory, and you have the back-to-work blues, David Bilkey might have a fix for you.
The University of Otago psychology department professor and Brain Health Research Centre director says the back-to-work blues are quite normal - and quite avoidable.
One of his areas of expertise is circadian rhythm - a 24-hour cycle in the physiological processes of living beings which Prof Bilkey believes plays a major part in people's mental health when they return to work.
"It's your body clock. The neural systems that controls when we wake up and feel alert in the morning, and when we feel tired at night, that's circadian cycle.
"And, of course, one of the things that we do when we go on holiday is we tend to sleep in in the morning, and perhaps go to bed later than we usually would.