Ultimately I think it's down to your personal preference and targets in life. For me I want to be able to work (because I enjoy work) but I also want to be able to spend lots of time with my wife and our, soon to be born, first child. So for me getting this balance right is key to my happiness. I'm sure there are countless other people in the same boat as me - work hard but at the same time want to spend valuable time with their family. The difficulty is actually getting it done.
Then there's the other side of the coin. There's the group that are very career focused, spend 10 hours+ a day at work and struggle to stop working when they leave the office. For these people their end goal may be money, responsibility, sense of achievement or any other personal driver they may have.
So who's to say which group is 'right'?
I don't believe there is a 'right' group - we are each able to live our lives as we please (one of the great things about living where and how we do). However, I do believe that when the balance is wrong for the individual it has drastic effects. Take, for example, someone who is stuck in a job they don't particularly like, having to work long hours for poor pay and the whole time they're missing out on what they really want to be doing. Alternatively, take someone from the other group who has huge responsibilities with friends and family that take up their whole time, restricting their career progression and ultimately their end goals.
Either situation is going to increase the stress your body is put through. Maybe not by a huge amount any one day, but that's not the problem. The problem is the chronic increase - i.e. a small increase but over a long period of time. This is going to impact your immune system, your digestive system, your emotions, your strength and fitness - pretty much everything you do.
What can you do about it?
Unfortunately there are times when there's not a lot you can do. But most of the time all it takes is a few steps to make small changes that make big differences.
1) Realise - you need to recognise that things are going how you want them to
2) Understand - what do you actually want?
3) Changes - write a list of small, achievable changes over a period of months that will help you hit your target
4) Measure it - set yourself a date to get the change done by and check you've done it
5) Move on - to the next change and keep going
All it involves is taking a little time to understand where you are, where you want to be and how to get there. Then it's just about making sure you take the steps to get there, rather than allowing yourself to divide your time up in a way that you don't like.
I hope this doesn't come across as preachy but if there's something that's driving our health and fitness into a downward spiral then chronic stress is going to be a big player. One way to help reduce it - get your work / play balance under control!