bite off more than you can chew

Tennessee WilliamsのThe Glass Menagerieを前に読みましたが、今度はBABY DOLLというThe Script for the Filmを読み始めました。映画になったようですが、名前も聞いた事がありません。古い映画なのでしょう。
THE CAR INTERIOR.
[They are jolting down the road.]
ARCHIE: Baby Doll, y'know they's no torture on earth to equal the torture which a cold woman inflicts on a man that she won't let touch her??!! No torture to compare with it! What I've done is!! Staked out a lot in hell, a lot with a rotten house on it and five complete sets of furniture not paid for...
BABY DOLL: What you done is bit off more'n you can chew.
ARCHIEは、19歳のBABY DOLLの夫ですが、BABY DOLLが20歳になるまでは本当の結婚ではない約束になっています。上に引用した最後の "bit off more'n you can chew" は慣用句の様なので意味を調べます。
"bite off more'n you can chew" という慣用句が辞書に載っていました。
・Cambridge Advanced Learner's English Dictionary: to try to do something which is too difficult for you: Clinton conceded, "We bit off more than we could chew in our original health care reform proposals."
・Wiktionary: (idiomatic) To try to do too much; to take on or attempt more than one is capable of doing.: I think I bit off more than I could chew when I agreed to paint this house by myself. Usage notes Often used as a caution, "don't bite off more than you can chew".
そう言われれば、今年の夏に手術する羽目になったのは実は歳を考えずに "I bit off more than I could chew." だったせいでしょう。