We rehomed our dog. It was a bloody horrible decision to make and 3 years on we still talk about her all the time and miss her terribly.
The ONLY reason we did it was a combination of our circumstances changing dramatically, and an offer of a place so, so much better for her. She has the best life now with a woman who loves and adores her. If that perfect offer hadn't come up we would have kept her and muddled on somehow, god knows how.
The way I see it was by getting a dog I made a commitment to her well-being for the rest of her life. By saying goodbye to her and letting her go to her new home I have honoured that commitment. It was the best decision for her, not for me!
We are still in touch. Dd still cries because she misses her.