To realize

The value of a sister:
Ask someone who doesn't have one.

To realize
The value of ten years:
Ask a newly divorced couple.

To realize
The value of four years:
Ask a graduate.

To realize
The value of one year:
Ask a student who has failed a final exam.

To realize
The value of one week:
Ask an editor of a weekly newspaper.

To realize
The value of one hour:
Ask the lovers who are waiting to meet.

To realize
The value of one minute:
Ask a person who has missed the train, bus or plane.

To realize
The value of one-second:
Ask a person who has survived an accident.

To realize
The value of one millisecond:
Ask the person who has won a silver medal in the Olympics.

To realize
The value of a friend:
Lose one.

-Anonymous

postScript: if you just realize....