Musar su Salmi 133:2

The author explains the prohibition of a private individual making anointing oil or incense, or even authorised people making up such incense in the amounts and proportions described here but intended for mundane purposes, as stemming from the fact that G–d has equipped the forces of the סטרא אחרא, the "left" side of the table of emanations, the side under the influence of Satan, with powers representing the equivalent or opposite of the powers of קדושה, holiness. We must therefore on no account provide those forces with additional ammunition by putting the tools of קדושה at their disposal.

"Concerning this matter, Moshe worried and said, 'perhaps I have, G-d forbid, made a profane use of the anointing oil?' A heavenly voice came forth and called out, 'as the precious oil on the head descends on the beard of Aharon.., as the dew of Hermon' (Tehilim 133:2-3), just as the law of profane use of holy objects is not applicable to the dew of Hermon, so also there was no profane use of the anointing oil on the beard of Aharon. Aaron however, was still worried. He said, 'It may be that Moshe did not transgress, but perhaps I have transgressed'. Another heavenly voice came forth and said to him, 'Behold how good and how pleasant it is for brothers to dwell together' (Tehilim 133:1) - as Moshe is not guilty of profane use, so are you not guilty of profane use".

Thus, we see that just like much contemplation is the way to acquire constant fear, so too interruption of thought and idleness of study is its greatest detriment, whether this is due to preoccupations or will - every interruption of thought is a nullification of the constant fear.