stern mommy

I have decided it is time to take action on one particular behavior that drive me nuts. Liliana has a bad habit about throwing things. Mostly her cup, plate and food off of the highchair but also toys. It isn't a casual toss but an aggressive throw. As far as the mealtime sport is concerned, I want it to end so she can be well behaved at other's houses or restaurants. When it comes to the toys, I just don't want her to hurt another child by hurtling a wooden xylophone through the air. So, I decided to enact the "naughty step" treatment. I have implemented this 3 times. Twice for highchair shot puting and once when she threw the wooden box of Melissa and Doug magnetic letters out of the toybox which landed squarely on my fourth left toe leaving a painful bruise. She is so obedient and good that when I pull her out of her highchair, explain what she did wrong, sit her on the step for one minute then come back she is still just sitting calmly on the first step with her hands on her thighs, waiting for me. At least the first two times. The toy box toss resulted in a loud scream from me (cuz that shit hurt), a not so calm yanking of baby out of the toy box and a stern plopping on the step. I explained and left. She was crying this time but she stayed on the step (she is so sweet). Bottom line is, I overreacted and shouldn't have punished her for that. I was reacting to searing pain. I feel so incredibly bad, almost 24 hours later about my behavior. It was such an overreaction and I am feeling so guilty that I scared her.
I am not good at doling out punishment. They say to be consistent but I can tell you, this is going to be really hard for me.