The letter associated with Kislev is samech, the circular letter that has a numerical value of sixty. Reb Nosson explains that samech alludes to nullifying negativity.
We learn this from the general rule that applies when non-kosher food falls into a pot of kosher food. If there is sixty times as much kosher food as the volume of the non-kosher matter that fell, its taste is nullified and the kosher food can be eaten. (If possible, the non-kosher matter must be removed, however.) The same is true regarding the negativity within each person. One way to nullify its “taste” is by focusing on the positive—by overwhelming it with “kosher” goodness.
King David turns to G-d in his Psalms: “Arov avdecha l’tov”—“Guarantee Your servant for good.” But the word arov (“guarantee”) literally means to “mix up” Your servant for good. The simple connection between guaranteeing and “mixing up” is that King David asked G-d to be involved with him to such a degree that He would take responsibility for him, like a guarantor gets mixed up with the borrower who takes a loan. B
ut we can also see this word as a plea to have G-d help us turn the proportion of our internal admixture of good and bad into an overwhelmingly good mix. Let the good within me outweigh the negative at least sixty-fold! I beg G-d to help me see that my positive powerfully outweighs my negative. I may recognize that I have to make repairs inside myself, but my main work is to maximize whatever good I can—that’s what nullifies the negative..
Dear G-d, please help me believe that You perceive only the positive, since You focus on the good. Please nullify mu negative thoughts and actions and help me improve myself through the power of positivity!