I had a reminder about this very topic just this week.
My very senior dog (GSD) woke up and couldn't hold herself up on her feet for more than a moment or two. As soon as they opened, I called the vet and rushed her in. I was beside myself with worry that today would be "the day." The vet determined it was just advanced arthritis and gave her medicine to make her more comfortable. He went to get her meds and was gone a long time and my dog was becoming more and more uncomfortable. He rushed back in and finally gave me her pills and I was ready to get her home to give them to her. There was a long line to check out - longer than I've ever seen there. Each person goes into a hallway with a half door one at a time (so that you can pay the bill without worrying about holding onto your pet). There were 4 in front of me - 3 people with dogs and a man, probably in his 70s, without a pet. He was right in front of me and I was really hoping that he would let me go ahead since my dog was having a hard time standing. She was visibly struggling. I tried to make eye contact but he wouldn't look at me. I was getting frustrated with the wait.
When his turn came, he took it. And then I realized, when he placed a small collar on the counter, that he had come in with a dog, and was leaving without his pet forever. I actually gasped. He wouldn't make eye contact with me because he was barely holding it together. He didn't notice my dog struggling because he had just lost his best friend And here I was, so consumed with myself and my problems that I didn't even see the obvious - this man was in extreme grief. I left in tears. I heard someone say that he had tried everything to save his dog and that he had cried so hard... I was leaving with my dog. He would never see his again.
And when the vet kept me waiting? Probably when he was helping this gentleman's dog cross over to The Rainbow Bridge. And I was impatient. Wow.
I vowed to stop making assumptions about people. The person driving too fast may have just been told that their loved one was in an accident. The rude woman in the checkout line may have a sick child at home and she's just in a hurry to get back to them. Point is... we don't know. And the compassionate thing to do is to not assume what you don't know to be true.