I think my favourite part is when the relationship is put to the test and despite what outside forces test them with, the couple is devoted to each other, believes in each other and has faith in each other. Like for example;
"Your significant other doesn't love you!"
".... I don't believe you. I KNOW they love me because I know them. If they truly wanted to betray me, they had more chances than I can count. They never did so and on top of that, they're there for me and make sacrifices for me. I'm not even angry that you said that because it's ridiculous."