Everyone, in some way, seeks to give their own life a purpose. Rather it be religion or a self-imposed sense of meaning, mankind must find a reason for being alive. If we do not, it is then conceivable that our lives are no more valuable than a blade of grass in a pasture.
We cling to that need to be someone. Where we gained these feelings from is anyone's guess. I imagine our ancestors didn't ponder whether or not they were important to the overall health of the universe. They were too busy discovering fire, finding food and simply surviving to question anything. Yet, whenever or however the need to understand our place in life evolved from is neither here nor there. In fact, it has become so ingrained in our basic being that it could not (at this point) be removed.
Therefore, the question now becomes: How do we define our life?
A simplistic answer is that we judge the value of our lives based on our experiences. The minute events that stand out to our psyche amidst a cacophony of perpetual boredom. I think I have just went from expose to melodrama in one sentence! At any rate, think of the past month of your life. Do you remember each nine hour work day you put in? Or do you remember the events that broke up that monotony?
My point is, in a roundabout way, experiences are what define who we are and how we have lived our lives. They differ for each person. While someone may think reaching level 100 on Warcraft is the pinnacle of that year, others (like myself) remember the day I went skydiving. But, as with all things, each experience is relative. The most important thing is that it reaches you and etches itself into your memory. I am loathe to believe that on my death bed I will look back and remember all the tedious work I did. The hours I worked to pay for a car, rent, utilities, health insurance, credit cards, student loans, car insurance, groceries and everything else we "require" to survive.
So, get off your ass and go do something memorable. You could scale a small mountain and stand by yourself looking at a waterfall. Head down to the old folks home and listen to a 100 year old man talk about the days when cars were first built or when Americans knew the fear of war. Visit another country and see their culture.
It is all there and it just for you. Our time here is finite. And whether you live 40 years or 140 years, it is imperative that you make each year something that will stand testament to the type of life you lived.