I love the title of this Harvard Business Review blog entry: "If You Don't Prioritize Your Life, Someone Else Will."
There's plenty of advice in the blogosphere about how you need to set your own priorities, decide what you want, map out a bunch of smaller steps to get to your set-in-stone goal, dream something to make it a reality. Yadda, yadda, yadda.
Then there's advice to the contrary. Sometimes the universe drops a nice surprise in your lap; be ready to take advantage. Seek serendipity. Be eager to make people like you (but don't brownnose). Offer value when you network rather than expecting to take, take take. Yadda, yadda, yadda.
Obviously you've got to steer a course between these two extremes. If you're headed toward an interview for a minimum wage job, and God drops a lottery ticket with "insant winner!" stamped on it for a million bucks--well, first verify it's legit (if it seems too good to be true, it probably is). But if it's legit, run like hell from the job interview.
With all the blather about what you can and should do about your future, this is a sobering reminder of the flip side. Other people want to own you. There are many, many people who want to claim your life for their own. Maybe some of your sense of obligation comes from inside your own head, projected onto someone else's agenda. The linked blog contains a story about a father who walked out on his wife and newborn in the hospital to attend an unproductive business meeting. He'll never get that time back with his wife and kid.
We all have stories, maybe none are as dire. You worked/studied so late that you were sleep-deprived and got in a fender-bender on the way to the event. You made a promise to a friend, and then succumbed to a string of "oh, and by the way, will you also...?" requests which totally chewed up your life. You signed up as a bridesmaid/groomsman, only to find the expected outlay of cash would take you a year to pay off on your credit card.
The linked blog also contains some suggestions about figuring out what's necessary, and when your own priorities should trump the socially-constructed sense of obligation nagging at you. Practice saying "no."
My own accomplishment (now that I'm 57 years old!): When the phone rings in the office, it's usually urgent. People use email for non-urgent business. But I have finally figured out that I don't have to answer the phone every time it rings--say, when I'm on my way out the door to a teach a class or attend a meeting for which I'm already late, or when I'm talking with a student about something emotionally sticky. I can let it go to voicemail.