Bhagavad Gita, Chapter 3 verse 39: Wisdom is veiled by the insatiable flame of desire which is the constant enemy of the wise.
‘Wisdom’ is knowing (understanding and experience) the separation of the Self from desire and the truth about the Gunas and their interactions (3.28). The wise let Nature do their desiring to further evolution through action. From the previous verse, the experience of separation is ‘veiled’ by desire. ‘Desire’ searching for happiness and contentment in objects of the senses is ‘insatiable’ because lasting happiness and contentment lie within, on the level of the Self, not in ephemeral objects of the senses; forever unsatisfied we get insatiably stuck on the cycle of impression-desire-action. The anger resulting from thwarted desire is like a ‘flame’ torching everything in its path (3.36 - 3.37). Thwarted desire is an ‘enemy’ upsetting the smooth and harmonious flow of evolution, which is the purpose of our existence.
Even the ‘wise’ who know the truth about the Gunas and their interactions should mind the potential for desire to overpower wisdom and stymie evolution; desire for attractive qualities found in objects of the senses is just that powerful. ‘Wisdom is veiled by the insatiable flame of desire which is the constant enemy of the wise.’ Even the ‘wise’ have to be on the lookout for temptations of their desire.