I cannot understand what it is about your post that is so egregious that it had to be downvoted three times (it was four but I cancelled one with an upvote), so I gave you 19 lingots to make you feel better about it. (Now let's sit back in our, er... mothers and wait to see how many downvotes I get for this post.)
Someone commented a joke above that makes the point that drunk mothers are like chairs because they're both under the table. So, my thought is that this new Duolingo expression would be said to a young woman or a mother, and basically means "don't be irresponsible." As in, don't get drunk; are not a chair, so don't put drink yourself under the table. The interesting thing is that contrary to popular belief, girls and women in ancient Rome weren't allowed to drink alcohol. In fact upon marrying her, the woman's husband was by law granted the right to kiss his wife with or without her consent whenever he felt like it specifically to make sure she didn't have alcohol on her breath. If he found out she'd been drinking, he could beat her no more or less severely than he would beat his own children.
Is is just me or is the speaker pronouncing it "sel-la-ey". I thought "ae" was a dipthong and pronounced as a single syllable "sel-lie". I marked the audio as not sounding correct, but maybe I'm mistaken on the pronunciation here? I feel like this speaker usually has solid pronunciation, so now I'm in doubt.