To realise

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 nine months:

Ask a mother who gave birth to a still born.

To realize
The value of one month:

Ask a mother who has given birth to a premature baby.

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.