得新弃旧dé xīn qì jiù

得了新人，就抛弃旧人：我知道你是个～的东西，白辜负了我当日的心。(八十·1992)不说薛蟠～，只怨香、玉二人不在薛蟠前提携帮补他，因此贾瑞金荣等一干人也正醋妒他两个。(九·205)

得新弃旧dé xīn qì jiù

off with the old love and on with the new; get rid of the old when one gets the new
❍ 我知道你是个～的东西，白辜负了当日的心。(《红楼梦》1049) I know you: off with the old love and on with the new—a poor return for all I’ve done for you!