It's hard isn't it. I can't tell you if you're on the right path, but I think some questions might help you decide.
- does smacking work? As in, does it help teach your DD1 what is acceptable?
- is it the most effective way of disciplining? As in, there's nothing else that works better.
- Can you stay calm when smacking?
- Have you and DH discussed the situations when you smack? (for example, you might smack for 'wilful defiance', that is, when the parent says 'no don't do that' and child looks at them with raised eyebrows and parent says 'no, please don't do that, or you'll get a smack' and then child does it anyway. Fair warning followed by consequence that 'speaks' to them most effectively at that stage in their lives. For forgetfulness when they're doing something naughty that parent told them about that morning, or when the child's overtired, then a parent won't smack in those situations.) If mum smacks and dad doesn't, then it's not necessarily consistent discipline, and I don't think the child learns 'that's not good to do, there's a consequence for that', they just learn who lets them get away with things.

I think we need to figure out what's most effective. I have a biter/hitter on my hands (as Ubba described, DS1 isn't a talker, and hits out in frustration - you have given me so much hope Ubba about when he starts talking!), and smacking isn't appropriate when he's frustrated/angry. That's something we need to address with some sort of down time.

Anyway, that was a bit garbled, ds is playing in the ottoman, so I'm just watching to make sure the lid doesn't crash down on him. But I hope it helped a bit? All the best working your discipline out.