No, I thought myself blest in being forgotten; knowing from Observation, that a great Man shews us a particular Kindness when he does us no Injury.
Every time the Count or another wealthy man thinks -- or claims -- that he is trying to help Figaro and do him a favor, Figaro ends up in trouble. A natural entrepreneur, Figaro is more successful when he's in business for himself.
According to the Perfections you fine Gentleman expect in your Servants, does your Excellency think many of your Acquaintance worthy the Office of Valet-de-Chambre?
A free man, Figaro speaks with shocking candor to his former employer the Count Almaviva. Figaro freely admits to being lazy, and does not deny that he had "a dubious character" while employed by the Count, yet he points out that the Count himself -- and most of the noblemen of his acquaintance -- are not exactly the pinnacle of honesty themselves.
I’d rather be too cautious then too secure.
A paranoid tyrant, Dr. Bartholo jealously guards his young ward and prevents her from seeing or talking to people. He has already spread a rumor that she is his wife, to prevent anyone else from courting her. Ironically, it is just this overzealous need for control that makes Rosine miserable. She hates Dr. Bartholo because she (rightly) believes he hinders her freedom.
Dr. Bartholo is suspicious of everyone: Rosine, his servants, Figaro, and every other character in the play. He is constantly convinced that someone is stealing from him, trying to cuckold him, or-- in Figaro's case-- padding a bill. Most of the precautions he takes against theft are completely unnecessary, but the precautions he takes are intolerable to the people around him.
If every Man has sufficient Charms to please me, whence comes it, I have so unalterable an Aversion to you?
Sick of the constant interrogation and cross-examination by Dr. Bartholo, Rosine turns his logic on its head. She is repulsed by the man who raised her, and who constantly accuses her and others of things they have not done. But instead of being emotionally broken by his ongoing verbal abuse and intimidation, Rosine has become strong and rebellious. At the moment, her rebellion has been quite minor: she's dropped a piece of sheet-music containing a note to a young man she saw singing in the street. But her statement and her rebellion foreshadow her decision to rebel against Dr. Bartholo as much as possible.
All cats, in the night, are grey.
Dr. Bartholo, at the end of his song verse, is repeating a French proverb about the relative unimportance of a romantic partner's appearance. At night, in bed, he believes Rosine won't be able to tell what her husband looks like, so his gray hair (or lack of hair) and elderly appearance shouldn't be a turn-off. The fact his behavior and treatment of Rosine makes her despise him does not enter into his calculations.
By my Faith, Sir, there’s but small Choice between a Fool and a Madman, and where I can’t get Profit, I’ll at least have Amusement; let’s be merry while we may, God knows whether the World will stand a Month longer.
Figaro lives for the moment and seeks to amuse and entertain himself. He doesn't expect to profit by the medicinal treatments he gave to Dr. Bartholo's servants and horse, but he justifies his actions because he found them amusing.
