Musar zu Jeschijahu 33:14

The sages already denigrated this trait and attributed it to the sinners, with many verses to support them such as "the sinners in Zion are afraid; trembling has seized the flatterers." (Isaiah 33:14). One of the great sages upon noticing his disciple afraid said to him: "you are a sinner" (Berachot 60a).

But the man who was completely purified from this affliction and has been cleansed of all trace of evil which lust leaves behind it, behold his vision will be perfectly clear and his discernment will be pure. He will not be swayed by any desire. He will recognize anything which is a sin. Even for the most minuscule, he will see its evil and will distance from it. On this our Sages referred regarding the men of Sheleimut (Wholeness) who purified their deeds to such a great extent as to leave not even a stirring of evil - "the clean minded men of Jerusalem" (Sanhedrin 23a).

You can now see the distinction between the Watchful and the Clean man. Even though both are similar in their matters, the Watchful is cautious in his deeds and sees to it that he does not sin in what he already knows and which is familiar to everyone that it is a sin.