の至り【のいたり】

の至り means "the height of": the feeling or state named by the noun has gone as far as it can. It follows a noun, almost always a Sino-Japanese word for a feeling – こうえい光栄, きょうしゅく恐縮, かんげき感激, せきめん赤面 – and ends the sentence with です or でございます.

These belong to speeches, award ceremonies and formal letters, where you thank someone or apologise. In conversation the same feelings are とてもこうえい光栄です or ほんとうに本当にはずかしいです恥ずかしいです. The pattern doesn't take everyday or concrete nouns.

若気の至り

わかげのいたり若気の至り is the exception. It means a foolish thing done because you were young and rash, and it is an everyday phrase used to excuse or own up to the past.