Aim at finishing the week (on Fridays) setting a clear list of priorities for the following week.

I do one key item per weekday, one thing only that I absolutely want to get done. Then I add a few reminders or secondary tasks (e.g., call this, email that, talk to them, send newsletter, etc.).

The few times I fail to do this, my weekend is not as relaxing as when I do it. And my weeks are not as productive.