"Another reason could be that the holiday was really good - you reconnected with friends and family, and most importantly with yourself. And now you're back at work and missing those connections, and even worse - starting to feel disconnected.
"A good way of dealing with this is thinking about what you want to bring back with you from the holiday. Was it walks on the beach that you enjoyed - well, take the time to still do them. Was it a pastime, a hobby, a connection that you want to keep up?"
Knight says it's good to decide what you want to keep doing even though you're working, and to assess monthly if you are still doing that thing or still in contact with that person. The reason for checking is it's so easy for the year to get busy and you forget the things that are truly important to you.
"Maybe what you've enjoyed is having creative time, listening to music, doing art or craft. Maybe you spent time in the garden and that was life-giving for you. Keep doing those things. Many people stop, and then look back and say 'oh, I just got busy'.
"If that's the case, you need to learn how to manage 'busy' otherwise life can get really hard. There's a price that goes with busyness, and that could be disconnecting from what's really important to you."
However, Knight says, there are people who look forward to getting back to work and say "I can't wait to get back to busy". The thing to remember is that there's nothing wrong with work - it's often about your relationship with work.
"If you are underworked, you are often bored and feel unappreciated. There's no growth and little work satisfaction. That could be a reason for having the back-to-work blues. Conversely, if you are overworked you can feel like you're never measuring up to expectation and feel unsatisfied with your performance and job.
"Both underwork and overwork cause undue stress. One of the keys to feeling satisfied in work is to have the right amount of challenge.
"Task variety is important. Most work should have task variety, meaning what you do includes the mundane, the menial and the interesting. The mundane can give breathing space. If everything's a challenge, it can get too daunting."
Knight also suggests that before going back to work from a holiday, prepare for it.
"It's a good idea to prepare for that first week. Make sure you have chosen your clothes for the week and the ironing is done. It's even a good idea to start waking up at work time for a few days before the holiday ends - that way you won't feel too sluggish at work. If you're already in your work routine, starting back up can be more relaxed and easy.
"Make sure you have enough time to get through the traffic on your first day back. Have your radio tuned to a favourite radio station, or good music to listen to on the way.
"On the night before you begin work again, don't stay up late and don't be hungover - that can make the back-to-work blues a lot worse.
"Be gentle about it and try not to get grumpy with the people around you, that can make it worse too."
Knight makes the point that often people blame work for their unhappiness, when that may not be the case at all.
"Ninety per cent of us will blame something or someone if we're feeling dissatisfied - and often it's work that we blame."
She says in some ways that's natural because we do spend a lot of time in the workplace. "People often see their work life as their life - not as something separate. Maybe a way of dealing with this is to reframe - look at active ways of transitioning between work and home life. Be creative."
But what if the back-to-work blues are about really being unhappy in your job? "That's about self-assessment," Knight says. "You need to ask yourself 'am I in the right place, is this truly who I am, am I cool with this? If not, am I selling my soul? Is it about work or something else? Am I giving enough to work and giving enough to myself too? Do I need to move on? And if so, what can I do about that?'"
Auckland's Dr Stress, John McEwan, says it's normal to love being on holiday as you have freedom, and it's also normal to have a revulsion for losing control. "Although there are some people who are happy to have controlled lives, most of us in the world love freedom."
When you go back to work, it's important to "fire yourself up", he says. "I take walks - physically fire myself up and throw myself into new tasks.
"You shouldn't dawdle back, because it's harder that way.
"If you have the back-to-work blues because you actually hate your job, you need to look at what you're doing and what plans you intend to make."
McEwan says it's important to be clear that it is your job that's the problem. "Make sure you're facing the right direction before you make changes - audit your life, the relationships, the social activities. Professionally ask the hard questions: what would I like to be doing, where do I want to be, is my current role a compromise? Do I have a plan? If you don't have one, make one - it feels better, gives you the power back."
