I realized once agin "as a mom, I should watch my mouth"

Yaya was cuddling me and whispering "mommy I love you" on weekends, while I guess she sensed I was in a pretty good mood too. All of a sudden, out of nowhere, she asked me"mommy, why sometimes you say some mean words?" I was shocked"what mean words?" She said"like once you said you would throw me out of the window if i don't listen.." Well, just for the record, it was over half a year ago, I must have been really frustrated with a crying baby(Peter) and a girl still very demanding after I met one of her requests after another, I lost my temper and yelled, "if you still don't listen, mommy will..." For that I have apologized for no less than five times, and I admitted in mind it was my fault. But still, Yaya seems unable to forget it. How should I control my anger if, say, I had a lousy day myself, while the kids just seem never give me a break? Anyway, "watch my words" especially in time of frustration is a sure thing.