I left out the following two sentences I varied. Thank you very much!

1) Macbeth hears a supernatural voice telling him that in murdering Duncan he has deprived his life of sleep.
2) He compares sleep to an innocent murder victim, to someone who repairs clothes, death, rest and cleanness after work, a medicine, the second course, that is the most substantial part of a meal.
3) He uses these metaphors to stress the fact that it is sleep which removes our cares, nourishes us and gives us life and energy as does the second course (not “as the second course does”?)
4) Finally, Macbeth admits that if he had to acknowledge his deed (he must know his deed /why is “must” correct if the following part is in the second conditional?) , then it would be best for him to lose all knowledge of himself.

2) You might like a semicolon for the last part as a complete sentence: second course, that is the most substantial part of a meal. OR change it to "second course, which is the most, etc."

either when it comes to the parentheses

4) must = should, ought to

You lost me with the "second conditional?" It's always best to quote the entire thing and then there is no doubt/confusion/question/quandry.

Sra