I spent years planning and preparing to get my first dog and I still wobbled in the first few weeks. I thought 'is this how it's going to be for the next 10 - 12 years?!' Those feelings do pass if you've really done your research and prep and picked the right dog.
Walking with a dog looked wonderful when it was theoretical. The reality, for an active dog, is that it's not as relaxing as it looks, keeping tabs on them and making sure they (and everyone else around them) is okay.
I love how he smells (even when he's wet) but the damage to my home from the hair he has shed is considerable (I have carpet). And he's not even a breed that sheds very much! Dogs also cause a lot of wear and tear on the interior of cars.
He is the very best thing ever, worth every sacrifice, but I have spent almost every day he is with me worrying about his old age and eventual death. This has been an exercise in hoping for the best but I definitely appreciate every day I have him.
The most surprising thing, for me, has been that he has taught me a lot about self-acceptance. I struggle with my weight. He doesn't but that's because I control what he eats. If he could, he'd eat and eat and eat. I figure, if the most wonderful living creature in the world can't self-regulate, maybe I'm not so terrible that I struggle with the same thing. I feel it's something we have in common and it helped me to be more compassionate towards myself!