詰めが甘い （つめがあまい、tsume ga amai ）

I've been teaching a TOEFL course for the last few months, and a friend of mine also teaches it in the room next to me.  We had our final class this week.  My friend forgot his textbook that day and was scurrying to the office to see if they had a spare copy.

He got the copy and we were about to go up to the classroom.  One of the ladies who works at the school (also a friend) was lingering in front of the office, and my friend explained to her that it was the last class and he forgot his textbook.  She laughed, "Tsume ga amai, ne!"  He and I looked at each other because we didn't know what that meant, but he somehow sensed something about it.  He said to her, "Kibishii!" which, in most dictionaries, translates as "strict," but these days we would probably say  "You're harsh," or something like that.  Our female friend / co-worker laughed.

We went up to class, and I entered my room just as one of our school's Japanese teachers was leaving.  I asked her what tsume ga amai meanst and her explanation was, "Tsume ga amakatta kara, sono ato shippai suru."  I understood the second half but not the first.  She was saying "Because you tsume ga amakatta, you'll fail."  So it set in that tsume ga amai is not a good thing, but I still didn't quite know what it meant.

Later on, our female friend / co-worker said that she looked it up in the dictionary, and tsume ga amai means "to slack off tpward the end."  I was thinking, "Oh, maybe kind of like fizzle out."  Basically, you didn't finish strong.  She continued to explain that it's kind of like someone who's playing chess, and he has the chance to checkmate, but he spaces out and doesn't do it, makes the wrong move, and so he loses the game.  

I had to laugh at that one.  The more people explained tsume ga amai, the more it felt like she was calling my friend a loser.  I Googled it and found another translation that sounded pretty good:  "You didn't follow through to the end."

I thought this was a nice visual example.