A person should always remember that he is here in the world for a limited period just to collect Torah and mitzvas, and he will eventually be rewarded accordingly. The evil inclination tempts a person when young to think he has plenty of time ahead, and this is a dire mistake, for each day is given to us to achieve different things, and one can not rely on tomorrow to do what needs to be done today. A person should see himself as a traveler from a far off land who needs to utilize every moment he has before he goes back.