Take a healthy break...

I sometimes got carry away in my Internet surfing - it got me all tired. I was looking for a free program to nag myself away from the screen. I found this one:

Userhealth
http://www.userhealth.tk/

According to the author:
"...The purpose of Userhealth is to be your silent health and sleep supervisor! What UserHealth actually will do is provide you with regular health, pause, and go to bed messages. The messages can be displayed like small popup windows in the right corner (Almost like a MSN login popup) or if you prefer a topmost window or just sound feedback. ..."

It pretty much does the job and is user friendly. However, the only downside is that it does not tell you how long a break you are recommended to take.