I can't claim to avoid attachment, maybe I try to avoid clinging since all things are impermanent. I am still in a dualistic mindset, clearly! If another sentient being such as a pet is in distress which cannot be removed or ameliorated, allowing a vet to end that suffering can be the greatest act of compassion possible. I have been in that position, the right choice is based on love, not on a selfish desire. Buddhism is said to fly with two wings - compassion and wisdom.