It gets easier.....a lot easier.
MuttDog was a bloody nightmare at first. We had a week of puking and pooing (every hour, one end or the other, 24/7) until I was almost halucinating through exhaustion. We put her on boiled chicken and rice. It got better.
Then we had the mouthing of me and DD. Lots of short sharp "OW" sounds and pushing her away. It got better.
Then the toilet training (ohhh the feeling of stepping your bare feet into a curly poo first thing in the morning ). Training pads, getting up and putting her outside at the first signal, lots of praise when she went outside and a sharp "no" if she tried inside - but no nose-rubbing, God no. It got better.
Then the chewing of DD's toys. We bought toys for MuttDog, lots of them (car boots are great) and made sure DD cleared up after herself (2 birds, one stone). It got better.
Then the lead training and recall. We used sound/scare rather than treats and it worked really well, better than my friend who use reward/treats (but I get that some people dont agree with it). It got better - she is hardly ever on a lead now, she doesnt need one!
The begging. "No" and pushed away if she begged - given some at the end of the meal if she didn't. She now sits next to DH and falls asleep when he is eating - never begs. So it got better.
Jumping on the sofa - ahh, well, we've kinda failed that one. In fact have pandered to her to the extent that she has her own end of the sofa that no-one else sits on. Hmmm... (
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MuttDog is our pride and joy, everything started getting better from 6 months onwards - now she is 2 and we are going to do it all over again. I still have my moments (bloody sodding dog hair on the sofa, waking up to doggy farts, muddy paw prints and fox poo rolling) but I wouldnt be without her and cruicially, neither would DH.
(what is it they say here? Oh yes, "This too shall pass")