These days there are real concerns about our getting too much exposure to sun and the risks of skin cancer. But there is also a downside to getting too little light, as anyone with Seasonal Affective Disorder (SAD) will testify.
People who go from car or public transport straight into an office, then to spend much of the day under artificial light, are denying their bodies the benefits of daylight on their skin and in through their eyes.
Internal offices and meeting rooms that have no natural light put an enormous strain on those who work there. How easy it is to become bored and lethargic in such an environment and to emerge with a headache. What chance of good business decision making under such conditions?
Even if it is a grey day or raining, make a point of getting out and seeing daylight (even if only for 5-10 minutes) to get the energy flowing again.
If you are running an important meeting where good decision making is needed, hold it in a room with natural light and ideally windows that can be opened.