Acharya Prashant explains that the difficulty in accepting the truth about close relationships, compared to professional ones like a boss, stems from the heavy investment of time, emotions, and future plans. When people are 'locked-in' to a situation for a long duration, the cost of acknowledging reality becomes too high, leading them to avoid investigating the truth altogether. He compares this to a financial investment with a long lock-in period and high exit penalties; if you cannot leave, you prefer to remain ignorant of bad news to avoid the pain of being trapped in a mistake.