Oh my God, I could outwrite an encyclopedia with problems my anxiety used to give my relationship.
Now it's fairly stable but at first, it was difficult. My bf is an extrovert, and he comes from a family of VERY outgoing people (and the family is BIG - his grandparents, parents, aunts, and cousins all live next door to eachother) - so outgoing that they really can't fathom people being introverted, much less shy and anxious. The first year or so, I struggled a lot because all of them including my bf couldn't understand why I was so frightened to eat dinner with them, or visit his house instead of him visiting me, or why I had trouble calling him, or why I was so quiet whenever we were in a big room. And even after I explained it, my bf still didn't understand why it wasn't ok to ask me to social events at the last minute and bring me into a big group of people I'd never met, or only met a few times.
It got so bad that his family actually held an intervention with him to try to get him to dump me and at least one member told him outright LIES to get him to leave me (saying I was f-cking around, that I was the reason he quit college, etc). And when he tried to explain that I had anxiety they just went "So!? Then she needs to get help. What's so hard about that!?" and he agreed with them. They just didn't get it and they didn't understand how debilitating my anxiety made me and how much WORSE it was when suddenly I'm pretty much expected to just snap out of it and become this friendly social butterfly among a huge group of people who are loud and boisterous and completely unlike my own quiet, conservative family.
But on the upside, they were right about me needing to get help, so I did. So in a way, all that stress did me some good. Now (5 years later) my bf is MUCH more understanding and more considerate to my anxiety problems, whereas before, he was just confused and frustrated. I'm not sure how his family feels about me, but they've eased up on me, at least. Since seeking help, my anxiety's improved a bit too - I can call him and go to his house to see him now, even though it still makes me anxious and I still avoid interaction with his family when I can. And I've gotten a little better at meeting the other people in his life. I don't panic as much as I used to.
I can't say things wouldn't have been easier if maybe I'd gotten with someone who lived with a quieter, smaller family because I think I would've adjusted into the relationship much more smoothly, but at the same time, I think the anxiety problems I had, that I don't have anymore, would've taken a lot longer to remedy. So either way, there's good and bad.