your own best doesn't cut it

Kotaro Isakaの小説 "The Mantis" を読んでいます。

'I can't set it up for you. You'll have to deal with him yourself,' Momo tells me, and then shares details on how I can get in touch with this Asagao. I never thought I'd be hiring a professional. 'If you really are going to go to war, make sure you cover all your bases. Don't just leave it all to another professional. There might be something you can do too.'
'I know.' In the end, the only one you can really count on is yourself. And if it turns out your own best doesn't cut it, you just have to accept defeat.


"your own best doesn't cut it" の意味を調べます。辞書の "cut it" の項に次の説明があります。

・Oxford English Dictionary: (informal) to (not) be as good as is expected or needed: He won't cut it as a professional singer.
・Collins Dictionary: If you say that someone can't cut it, you mean that they do not have the qualities needed to do a task or cope with a situation.: He doesn't think English-born players can cut it abroad.
・Wiktionary: To suffice; to be effective or successful.: Sometimes, professional tools are necessary and homespun solutions just don't cut it.
・Cambridge English Dictionary: to not be able to deal with problems or difficulties in a satisfactory way: If he can't cut it, then we'll get someone else to do the job.

"cut it" は普通は否定形で使われるのですね。"your own best doesn't cut it" は「最善を尽くしても見込み通りには出来なかったら」の意味でしょう。