Pack your bags, you're going on a guilt trip.
Q: Why?
A: Because you're a loving father mate.
Sorry LT, but it proverbly won't be the last time you make her cry.
My dad was quite tough on my siblings and I when we were growing up and when were very naughty we were smacked.
(Not beaten and always only on the butt.)
I remember afterwards my father would say to me,
"You know that hurt me more than it hurt you."
At the time I didn't believe him, but as I am a father now myself, I can easily understand the truth in what he was saying.
He loved us kids and making us cry did hurt him more than our punnishment hurt us.
He also taught me through discipline that there are consequences for your own actions and bad behaviour, which taught me "right from wrong" and shaped me for the better to the man I am now.
(I loved my dad, but I also feared him when I was naughty and that kept me behaved... Well most of the time anyway.) 
Besides kids do cry, it starts at birth and later often its over trivial matters or when they can't get there own way, so don't be upset with yourself too much.
Cheers,
Dave