Based on Bhagavad Gita Chapter 06, Text 44
As aspiring devotees our devotional determination may waver when we are confronted with temptations of material pleasures.
Often these pleasures haunt us like ghosts; they keep popping up again and again, possessing our mind and pushing us to act in distressing or even disgusting ways.
If due to this repeated pushing we give up our devotional principles and indulge in those pleasures, we will find them strangely insipid. Even if we seek those pleasures in grosser forms and with greater frenzy, still the same tastelessness will dog us relentlessly.
Such tastelessness, Gita wisdom informs, is a sign that we are haunted by another ghost: the ghost of devotional happiness. The great Vaishnava commentator Vishvanatha Chakravarti Thakura uses the ghost metaphor to convey the unforgettability of spiritual happiness. Unlike the ghost of material happiness that torments us at the conscious level, the ghost of devotional happiness usually acts at a subconscious level. There, it exposes the emptiness and hollowness of all material pleasures by contrasting them subliminally with devotional joys.