As they say, too much of a good thing is also bad for you. Everything has an optimal level.
What is an optimal level you ask? Well it is the idea that you need a certain amount of something and no more.
Attribution: Wikicommons - Mikael Haggstrom
To use the example of stress: if you are very relaxed the quality of your work will be lower. If you increase the stress level a little you will do better, and a little more stress and it will continue to increase. However too much stress will cause you problems.
Let's look at some typical health related examples.
Currently there is a big trend with protein supplements. Mostly because they can take whey (the waste product from making cheese), and sell it to body builders at a huge profit. However many people are now suffering liver damage from having too much protein.
Another example is of course vitamins. When vitamins were discovered they were suddenly able to cure all sorts of health problems. Some people figured, if a little bit of a vitamin will cure some diseases, other diseases can be cured with lots of the vitamin. Of course all this was based on very little evidence, and research has often linked high dosages of vitamins to increased health risks. That is, too little of a vitamin is bad for you, but so is too much.
Then there are all the unhealthy things we are meant to cut out of our diets. Lack of salt, fats and carbs all have negative impacts on our body. Our goal isn't to cut them out of our diet but to have them in an optimal way.
How to be optimal
Olympic athletes actually use a training schedule so that they peak for the Olympics. For the rest of us it is much simpler. A lot of the time we hear this referred to as balance, but it can be better dealt with in terms of optimal levels.
Attribution: Flickr - James Jordan
How many hours can we spend at work and still be productive? Many people who spend ten or more hours at work often do less work in their day than people who are just in the office for seven or eight hours. The reason being of course that they are both tired, and use some of those ten hours to do other activities and be social (the latter causing other people in the office to lose productivity).
Then there is exercise. A friend took up cross fit and he became so excited he was going every day. I warned him about burning out but he dismissed the idea until the following week where he told he how his body now felt completely exhausted. He now goes to cross fit three times a week and usually does yoga on the other days.
The easiest way to achieve optimal level is to have variety in your life. That way we can easily push ourselves in one area and change when we feel we are becoming over burdened.
I like this at work, where I can spend half the day working quietly on my computer and half the day dealing directly with people. If I have to spend the whole day doing one or the other, I often feel I am just wasting my time and lose a lot of productivity.
Add a little science
Most commercial organisations want you to consume as much of their product as possible. Fast food places want you to come back everyday whether it is healthy for you or not, and the health supplement people want you to use lots of their product with the same attitude.
There is plenty of information about healthy levels of most foods and nutrients. It makes as much sense to restrict your sugar, salt and other intakes as it does to restrict vitamin and nutrient intakes.
Exercise is more difficult, yet thanks to the various heart rate monitoring devices we can now easily exercise at the level that best suits us.
So whatever aspect of your life is causing you stress, or if you're lacking motivation and productivity, work to find your optimal level.