There was a king named Bharata, who lived his life following nishkam karma-yoga while doing everything needed as a king for his subjects. When he got old, he handed over the kingdom to his son and left for jungle, living life as a sanyasi.
While living in the jungle, one day he saw an injured deer coming towards him, and she died giving birth to the baby. Given that baby deer was small, Bharata took pity on him, started to take care of it. During this time, he developed an affection for the baby deer, such a way that, if the deer is out of his sight he would start to worry about him.
When the time came for Bharata to die, his only worry was ‘who will take care of my baby deer’. Due to the unfulfilled desire, Bharata was born as a deer himself next life.
Finally, when he got to become human again, to not repeat the mistake of last time, he pretended to be a fool for the whole of his life, even though he was getting ill-treatment from everyone around. But, given that he was determined not to fall for desires, he endured suffering but did not budge.
In summary, due to one desire of taking care of the deer, Bharata had to go through multiple lives, and pain. Think about what would happen to all of us, who have thousands of them, with new ones forming every second.
As Mundukya Upanishad says
,कामान्यः कामयते मन्यमानः स कामभिर्जायते तत्र तत्र । र्याप्तकामस्य कृतात्मनस्विहैव सर्वे प्रविलीयन्ति कामाः ॥ (2.3.2)
Whatever one desires with the eagerness of mind, he/she is born in those places, but one who has won over all the desires does not get additional birth, as there is nothing to left to achieve.
Bhagavad Gita too has not-so-kind words for it.
काम एष क्रोध एष रजोगुणसमुद्भव: || महाशनो महापाप्मा विद्ध्येनमिह वैरिणम् || (3.37)
Desires are the most sinful enemy of this world, they get generated through raja-gunas and give rise to anger (ruining human lives).
But, can we really give up desires?
Maybe not, but in my experience, I have found it easier to trick the mind, to make it pick new desires while dropping the old ones. For example, while giving up the worldly desires, pick up spiritual ones, that way mind has something to latch onto while we make spiritual progress. Need some practice, but worth the effort.
All the Best!