Use of the subjunctive mood

I wish my cat were more fit. If he were fitter, he could run faster and jump higher. It's necessary that he not eat such*quantities of biscuits. Sometimes, I say to him, "Cat, it's vital that you not be so fat.** I want you to eat less than that" or even, "Cat, I hope you exercise every morning,** it's imperative that you catch lots of mice". My wife said to me yesterday, "I would like the cat to not be so lazy** it's necessary that you be less generous when you feed him! I suggest that both of you go out for a walk every morning and that you return home before 9 o'clock!

* The use of "such" here is unclear, since you have not yet established what "such" refers to (e.g. small?  large?).

** A period would work better here, since these are two independent clauses.  Joining them with a comma would be a "comma splice".

good job!

Use of the subjunctive mood

I wish my cat would be fitter. If it was fitter, it could run faster and jump higher. For that to happen, it's necessary for it not to eat high quantities of biscuits. Sometimes I say to it: "Cat, it's vital that you not be too fat, I want you to eat less" or sometimes: "Cat, I hope you exercise every morning, it's imperative that you catch a lot of mice". My wife said to me yesterday: "I would like the cat not to be too lazy, for you should be less generous when you feed it! I suggest you both go out for a walk every morning and that you be at home before 9 o'clock!

Use of the subjunctive mood

I wish my cat were more fit. If he were fitter, he could run faster and jump higher. It's necessary that he not eat so many biscuits. Sometimes I say to him: "Cat, it's vital you be not so fat, I want you to eat less than that" or even: "Cat, I hope you exercise every morning; it's imperative that you catch lots of mice". My wife said to me yesterday: I would that the cat be not so lazy. It's necessary that you be less generous when you feed him! I suggest that both of you go out for a walk every morning and you be at home before 9 o'clock!

I tried with this one, Guy, but the subjunctive mood is not my forté, so I may very well have made some mistakes. It is an old English form and if you choose not to learn it then you can easily live without it. For instance, in modern English, one would write: You should be less generous when ..., or, cat, it's vital that you should not be so fat. etc. May I ask why you learn it?