We make the mistake of thinking that Nishmas is something that you only say shabbos morning, psukei dezimra, part of davening.
But Nishmas is a holy compendium.
It's a holy, holy tefillah.
It's a long, poetic, magnificent expression of gratitude. The Ben Ish Chai writes:
You're going through a whole time. One of the things to do is pledge and promise to Hashem,
"Hashem, if/when you get me out of this, I'm gonna say Nishmas slowly and sweetly and sing it to you and thank you for it."
