These days I read something interesting that explained why we need breaks during the day between tasks or concentrated activities!
As you know, we have different stages of sleep and one cycle takes around 90 minutes.
The interesting part is that we also have these 90 minute cycles during the day in wich our performance varies. Therefore, by nature, our body takes 15-30 minute small breaks in between activities - if we allow it!!
You can notice this need when you start yawning, your mind gest distracted, you get tired, loose concentration, etc.
Certainly you can postpone these breaks but if it happens on a regular basis, your body will start complaining with stress-symptoms.
Start listening to your body and research a bit about chronobiology. It's quite interesting!