I remember in Art School several professors told us NOT to say we didn't finish a drawing, painting, or other assignment because we were working on an English paper, and yet students inevitably did. Which was funny, because they were Art Majors too. Their Art projects should have had top priority since that's what they were pursuing as a vocation. I'm guessing it was years of brainwashing from the public school system instilling a sense of "important" and "unimportant" and Art was pushed to the backseat.
There will always be more things vying for our attention than we have time to give. Some are important. Some are less important. Some are urgent, and some can wait. If we make a grid with these attributes, we see four categories emerge. The items in the urgent column seem to get done, because there is a pressing deadline. That's good until we realize we tend to sacrifice things that are important but not urgent for things that are unimportant but urgent. The important things that aren't urgent are the ones that get swept under the rug. These include things like improving our skills, spending time with loved ones, and other self-improvement and family improvement activities. Hence the importance of priorities.
Other times we may let others determine importance thru deadlines. Deadlines are a powerful motivator. If you never set a deadline for a task, you'll probably never complete the task, because you can always do it "tomorrow" and instead focus on things that can't be put off. Deadlines are an important and powerful tool, but like any tool, they can be used for destruction as much as construction. To avoid this, one needs to discriminate between the important and the unimportant and be willing to ignore the unimportant even if negative consequences follow. One should also realize many deadlines were contrived and can be pushed back without serious difficulty.
One must look at the important but nonurgent tasks and set aside a time to do those. Set a deadline and make them urgent, even if it's artificial and contrived. It will cause conflict with other taks and induce stress, but in the long run you will be grateful you did it. The alternative is looking back with regret, and who wants to do that?
The comic above is a page from Wandering Koala Digest 2 and a perfect illustration of a typical student/worker/person who did not exercise proper discrimination. He traded the urgent but less important for the less urgent but more important. I drew it with a Zebra disposable brush pen and colored it in Adobe Photoshop. Let me know what you think!