Here is one sentence-example from my grammar book:
"I
should kill myself today if I didn't believe that tyranny and injustice must end."
My grammar book says that
should is used with the first person singular and plural,
would is used with the second and third persons singular and plural.
But may be I can use
would:
"I
would kill myself today if I didn't believe that tyranny and injustice must end."
Is the last sentence correct too?