Cats are rather delicate creatures and they are subject to a good many different ailments but I have never heard of one who suffered from insomnia.
A fanatic is one who can't change his mind and won't change the subject.
The poets have been mysteriously silent on the subject of cheese.
The public character of every public servant is legitimate subject of discussion and his fitness or unfitness for office may be fairly canvassed by any person.
When a subject becomes totally obsolete we make it a required course.
I have always felt that a woman has the right to treat the subject of her age with ambiguity until perhaps she passes into the realm of over ninety. Then it is better she be candid with herself and with the world.
If you are ever at a loss to support a flagging conversation introduce the subject of eating.
None of my own experiences ever finds its way into my work. However the stages of my life - motherhood middle age etc. - often influence my subject matter.