自分が堅く誓ったことは、どんなことがあっても実行しなければいけないよ。

myself; yourself; oneself; himself; herself; I; me; you

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

hard; solid; tough; stiff; tight; wooden; unpolished (e.g. writing); strong; firm (not viscous or easily moved); safe; steady; honest; steadfast; obstinate; stubborn; bookish; formal; stuffy

to swear; to vow; to take an oath; to pledge

thing; matter; incident; occurrence; event; something serious; trouble; crisis; circumstances; situation; state of affairs; work; business; affair; after an inflectable word, creates a noun phrase indicating something the speaker does not feel close to; nominalizing suffix; pretending to ...; playing make-believe ...; alias; aka; nickname; alternative name; also known as

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

what; what kind of; (with -temo, demo, etc.) any(body, thing, means, etc.)

to be (usu. of inanimate objects); to exist; to live; to have; to be located; to be equipped with; to happen; to come about

too; also; in addition; as well; (not) either (in a negative sentence); both A and B; A as well as B; neither A nor B (in a negative sentence); even; as much as; as many as; as far as; as long as; no less than; no fewer than; even if; even though; although; in spite of; further; more; again; another; the other

practice; practising; performance; execution (e.g. program) (programme); realization; realisation; implementation

indicates certainty, emphasis, contempt, request, etc.; used when calling out to someone; used to catch one's breath or get someone's attention; yo!