ずじまい

ずじまい means "never got around to it": you meant to do something, the chance passed, and it never happened. Take the ない-form and replace ない with ずじまい – 言わない gives いわ言わずじまい, 見ない gives み見ずじまい. It almost always looks back on something already over, ending in だった or になった, and it carries regret.

• × しずじまい → せずじまい

With a potential verb, ずじまい says the chance never came, rather than that you put it off.

In the middle of a sentence, ずじまいで is "without ever having done it", and the rest says what happened next.

ずじまい is written and a little formal, though you hear it in conversation too. The plainer way to say it is けっきょく結局から～なかった or 〜～ないままおわった終わった.