Smoking and being way too in love with alcohol. I dated a guy who could not fathom the fact that I wasn’t keen on partying or getting drunk. The main pastime for his entire family was drinking. And smoking. He didn’t smoke himself but got into the whole “smoking while drunk” thing cos all his cousins did it, and when I told him I couldn’t deal with dating a smoker (which I had already mentioned to him before we started going out), he promptly broke up with me so he could continue his habits. Charming. Oh and did I mention that he was a climate change sceptic and his dad hunted animals for fun? He actually had stuffed heads of antelope and deer etc hanging on their walls at home - I was so creeped out.