Have you ever been on a cruise? If so, you will know that when you are allowed ashore you may entertain yourself by looking around and doing some shopping, but you should always be aware of when the ship will depart, lest you end up stranded where you don't belong.
The same goes with life. It's fine to enjoy its pleasures and to entertain yourself a little. But you should always keep in mind that at some time the voyage will be over, since it does not last forever. When the time comes, be ready, and make sure you look back and do not find that you have misspent your shore leave.
The best way to avoid this is to ask yourself from time to time what is important, and to act accordingly. . . . Cultivate, then, an attitude of equanimity toward externals.
-Massimo Pigliucci, A Field Guide To A Happy Life: 58 Brief Lessons For Living