Being online can allow us to lead an extremely productive existence with the things that we can get done. However, there are some things that will eat our time up. To be fair, there are some things that will eat up our time offline as well.
One of those things though is constant checking our e-mails. Sometimes when people expect a message, they hang around the area of the e-mail checking it. Not knowing that it burns up a lot of time during the day.
I try and make designated times where I check my e-mail during the day. When I get up, one time in the middle of the day, one time in the early evening, and one time before I shut down seems to be good. Of course, your schedule may vary depending on what happens offline.