gracesgran I find it interesting that you mention marketing. I lost a job because I flatly refused to go out selling when the business was suffering, I knew I just couldn't do it. I too am confident but reserved. I like my own company, I am not bored. I have friends who are constantly going out, as if they are scared to be on their own. It's taken a while for friends here to realise I don't want to be out socialising all the time, they don't try to push. I don't find going out an effort at the time, not at all, it's taken years to realise why I am so shattered the following day. I just find social interaction with people I don't know well exhausting, and it takes me a long time to relax in their company. Not that they would ever know it.
And yes - some people are hard work. You ask a question, hoping to find common ground and all you get is Yes or No in reply. Maybe because they are desperately shy, but you need more, you can't just stand there asking, do you have any children, where do you live, how do you know the hostess/host, or what year is your child in, without any feedback at all, because then you start to sound like a hairdresser as you ask where they are going on holiday.