How would you feel? We have a child-gate to separate our cat and dog. The dog is a terrier, and chases cats. We had a pet each when we met, and have used this solution for a long time with no issues. The cat is 21, and so, stays in mostly, but is taken for tours around the garden when the sun's out, and the dog is contained. We are all 4 usually very happy.
I just came back from walking the dog, fully expecting that the cat would be safely enclosed. My partner was expecting me at around that time. The dog went hurtling in through the door, as always... and the cat is wandering about, loose, in the hallway. I had to do a goalkeeper-like dive to stop the terrier getting at the cat, which would have been a very dangerous situation, given the fragility of the 21 year old cat. My partner said 'Oh, I left the gate open, I didn't realise the cat had even walked out', and did apologise, but...
I'm upset. The risk was enormous. My partner was so careless. An apology makes no difference, when my concern is the lack of awareness of risk.