F.lux is a free software that reduces the amount of blue colors on your screen in the night hours. Their slogan is "software to make your life better", and that's pretty much what it does.
Before i got F.lux i could get tired after 6 hour sessions of music production. After i started using F.lux i can sit on my computer for days (I run it at max setting all day long). If that's a good thing will have to be up to you =p
You can get F.lux for free @ https://justgetflux.com/They have versions available for Windows, Mac, Linux, Iphone/Ipad & Android.