Dicipline oh no!

OK so yesterday after I took Lani outside to play with our neighbor for a while when we get inside to take a bath she says "NO" and I told her yes that she needed to obey, well she started to throw a fit. I knew she was really tired because she hadn't taken a nap and just got done playing in the heat for an hour or more, so I tried to be easy on her but my patience was running low. She had thrown a fit the day before with her dad and we decided that her punishment was going to be taking her favorite doll away for a day and then she did this again. Oh no! How this breaks my heart to have to spank her, but I did! I spank her, she was still crying and saying no. I was getting angry and going through my head was the words of some moms from the moms group telling another mom to up the spanking. It made me think that maybe I'm too soft and I also needed to do that. So I spanked her again and this time it really hurt her she grabbed her thigh and started telling me how much it hurt, I grabbed her out of the bath(because I was trying to give her a bath, I dont think it was such a good idea of my part) wrapped her up in her towel and loved on her. I felt so bad, almost convicted of what i did. Did I do it out of anger? Did I do it because I was trying to be like other moms? I don't know, all I know is that i thought about it all evening until Eliott got home and then I cried about it to him. I realize that I am not other moms and that if other moms want to only use that form of discipline that's them. I realize that to some moms or dads what maybe ok for me maybe not be ok for them. I will keep trying to do other forms of discipline with my child first. I prayed and ask God to forgive me for the wrong motive of my heart and I decided to do further studies on the subject. I found this good website dougbrittonbooks.com that had a good study on discipline based on the bible. For now this is what I got so far. Hope this can also help other moms struggling out there.