Acharya Prashant explains that the difficulty in letting go of things, thoughts, or people arises because we are the ones clinging to them for specific reasons. He notes that humans are rational beings who maintain attachments because they have convinced themselves of their necessity. When one tries to drop an attachment without addressing the underlying reason, it leads to an internal conflict where one reason fights another. This results in an endless inner civil war and a swing of moods where no decisive victory is ever achieved, leading to constant effortfulness and strife.