Mencius - Book 2, Part 2, Chapter 13

When Mencius left Ch'î, Ch'ung Yü questioned him upon the way, saying, 'Master, you look like one who carries an air of dissatisfaction in his countenance. But formerly I heard you say "The superior man does not murmur against Heaven, nor grudge against men."'

Mencius said, 'That was one time, and this is another.

'It is a rule that a true royal sovereign should arise in the course of five hundred years, and that during that time there should be men illustrious in their generation.

'From the commencement of the Châu dynasty till now, more than seven hundred years have elapsed. Judging numerically, the date is past. Examining the character of the present time, we might expect the rise of such individuals in it.

'But Heaven does not yet wish that the kingdom should enjoy tranquility and good order. If it wished this, who is there besides me to bring it about? How should I be otherwise than dissatisfied?'
~ James Legge translation via nothingistic.org ~

Go here to read the introductory post to this serialized version of the Works of Mencius.