丢三落四
[词典] forgetful; （形容马虎或记忆力不好而顾此失彼） miss this and that; forget this, that and the other; there is always sth. [sb.] missing;
[例句]把你娶媳妇应办的事早些料理料理，免得到时丢三落四的。
You should make preparations in good time for your own wedding. We don't want to find, when the time comes, that we've forgotten this, that and the other.