1. A person, who is crooked, can never enjoy real peace of mind.
2. A person, who is crooked, can never enjoy -a- real peace of mind.
Do you consider the article - 'a' is a must or we can leave it.
Could you please guide me?
Words like peace of mind, inner peace, happiness etc. are rarely used with "a". Only when they are followed by "which" or "that". For example, he felt a peace of mind that he had never experienced before.
Not to be confused, of course, with a piece of mind (as in he gave her a piece of his mind = he told her off, he expressed his anger at her).