It's been my experience that people's goals fall into one of three categories.
The first are long-term goals. They can be abstract ("I want to be rich") or concrete ("I want $1,000,000 at the end of ten years"). They can affect the world ("I want to eliminate poverty") or they can be centered in your little corner of the universe ("I want to live in luxury with my family").
Our long-term goal(s) defines who we are, although not necessarily consciously. If you've ever had a mid-life crisis and question what your purpose in life is, a long-term goal can provide you with that satisfaction. Similarly, long-term goals can manifest itself in other terms like religion, faith, purpose, calling, politics, or agenda.
A person's long-term goal isn't readily apparent. I think every person starts out with the same objective: finding out what our long-term goal will be. There's no definite time frame for this. Some people discover their answer at age ten. Others at age forty. During this time, we're focused on the process of discovery rather than fulfilling a specific agenda.
By their nature, long term goals are difficult to achieve and we won't see results immediately. That's both good and bad: on one hand, we'll always have something next to drive us forward. On the other hand, it can be a frustrating experience as we don't get to experience tangible results (although completing short-term goals related to your long-term goal can be satisfying). It's also entirely possible that we may never achieve our long-term goal but at the end of the day, it's the striving that matters.
For example, in my case, my current long-term goal is to a) promote Philippine speculative fiction, and b) be involved in the publishing industry in some way. The former has been constant (although I might change it in the future to be more inclusive of others). The latter has honestly changed over time: before I wanted to have x books published by year xx. It's altered mainly due to my current activities and relation to my first goal. I don't mind being an editor and nurturing other talent for example. When I need to get my life back on track, I recall my long-term goal.
The second are short-term goals (note that I use short term relative to long term: a short term goal can take a year to complete for example). They can be arbitrary goals ("Earn enough money to buy an iPad") or they can be related to our long-term goal ("Finish writing this short story").
Short-term goals can be very fulfilling, especially when we achieve them. They're usually how we measure our success. Problems crop up when we have too little short-term goals that are related with our long-term goal. For example, as terrific as winning ten consecutive games in Starcraft 2 feels, it honestly won't help me in my goal of establishing a career in speculative fiction. Another problem is misinterpreting how important our current short-term goals to our long-term goals are. For example, in my case, is conducting my nth author interview really helping me as a writer? (It might or it might not. Distinguishing the point when it does and doesn't is important though, and some people still continue pursuing an activity even if it's now irrelevant to their goal.) Or we could simply be swamped with too many pressing short-term goals (i.e. work) that we lose sight of the bigger picture.
I think it's entirely possible to live a happy life simply by completing a lot of short-term goals that are unrelated to your long-term goal. When you stop to reflect, however, you might not be satisfied with what you discover.
The third kind of goal is what I'd classify as a "side quest". It's not quite a short-term goal (it can't be completed immediately) but it's not as essential as a long-term goal. For example, in my case, this takes the form of romance. Despite my rants for the past month, I'm fine living the life of a bachelor (and I've even imagined dying single). But when someone interesting comes into my life, courtship takes on the form of a long-term goal (and anyone in a relationship knows it doesn't end with marriage) and there are various short-term goals I know that I need to take (first date, second date, etc.).
Unlike long-term goals, it's possible to quickly meet failure with "side quests". Again, it's not essential to who you are, but on the other hand, failure in this endeavor can feel just as devastating (and this isn't just failure as a short-term goal but failure in a series of short-term goals). On the other hand, this can morph into a long-term goal (not applicable to romance but some other "side quest" such as the charity you're a patron of taking up much of your life).
What are your goals? How does it come into play as a reader and/or writer?