Time is valuable. As it flows on, nothing can stop its course. Time once past cannot be brought back by any means. But, many do not realize this. They waste their time, thinking that they would make up the loss in future. The hope, however, is never realized. Thus, if anybody wastes his boyhood/her girlhood, he/she will not be able to acquire and build up character in future. And will suffer all his/her life in consequence. Similarly, if a student neglects his/her studies from day to day, no amount of hard work before the examination will get him/her through.
If we look around we shall see that the successful men/women in all spheres of life are those who made proper use of every moment of their time. The most prosperous nations too are those that do not waste any moment. We also should take our lessons from them both ourselves and for our nations.