Having an idea of what you want to accomplish is the first step in success. Setting some sort of goals or targets gives you something to focus on. What I love about defining this for a week, or a day even is it forces you to create something realistic.
With a large timeline these typically become unwieldy - it's hard to predict what you can do in 6 months. It's much easier to say what you can get done in a day.
And it's all good to have long term goals, it's just more important to focus on what you can do today to fill that goal.
And when you start setting these micro goals they become easier to obtain. Goals like the following are clear, focused, and achievable:
Play the guitar for 20 minutes
Bang out 25 pushups
Compliment one person
And the point is to create these daily goals you can knock out. Sure, one day of strumming away for 20 minutes isn't going to turn you into Jimi Hendrix, but do this day in a and day out and the end of All Along The Watchtower will one day start to seem not that far fetched.