When do you know you have done enough in life? Is it when you die, does that mean you have fulfilled everything that you can possibly do? What if you feel death coming about, but you don't feel that you have done enough?
When you are young, you feel that your life is a really long time. Seventy plus years seems like a really long time when you are only 6 or 10, even 13 or so. When you are young and haven't experienced "real" life, you beleive that you will live that long. In reality, a life can be as short as a few minutes, months, even a few short years.
In your young age, you feel that you are invincible and can do whatever whenever because you're not going to die anytime soon, it just doesn't happen that way. Some day you are faced with the truth, and realize that you should have spent your time a little more wisely. Now, how is the best way to spend your years? You think that maybe you should have been a little nicer to everyone, helped the less fortunate, spent a little more time with the ones you care about.
Everyday life involves so many people. In just one day, you touch so many people. It could be the passing smile you give someone, a kind word, or maybe something special you did because you wanted to, not because you felt you had to. So in the end, no matter how you spent your time, you reached more people than you can ever realize. That passing smile could have been the one thing that brightened up someone's dreary day. The kind word could have been the reassurance that person needed.
Everyone's life has so much more meaning than they can ever imagine. Keep spending your time just being you, and there won't be a wasted moment.