Should we forget or just need reminding, then the following quotes say it all… 

“Sometimes the most productive thing you can do is relax.” 
Mark Black 

“While there’s nothing wrong in being very productive (kudos to you!), your brain still needs some rest to be fully operational whenever you need it.” 
Debeena Harris, Mindfulness

“Show me a worrying person and I will show you a person who does not know how to relax.” 
Albert E. Cliffe 

“No matter how much pressure you feel at work, if you could find ways to relax for at least five minutes every hour, you’d be more productive.”
Dr. Joyce Brothers 

“Every now and then go away, have a little relaxation, for when you come back to your work your judgment will be surer. Go some distance away because then the work appears smaller and more of it can be taken in at a glance and a lack of harmony and proportion is more readily seen.” 
Leonardo Da Vinci

“Take rest; a field that has rested gives a bountiful crop.” 
Ovid 

“For fast-acting relief try slowing down.” 
Lily Tomlin