In a job you have an aim, to do whatever your job is; and interactions with colleagues are to help achieve that. That you get on well with some is secondary, and so there is little in the way of trying to be sociable and liked. A social situation is different. There the whole aim for many is to shine and win approval, which is a lot of pressure for someone who didn't naturally gain social skills and thus feels awkward and self conscious. Plus you have to make an effort to attend and interact in a social situation whereas you have a need to discuss things about work so there's no prior though about finding a subject to discuss. If you eased off at feeling any need to impress, and be more aware that others are more concerned about how they come across to other, than to pass attention to how others are coming across, social situations become easier. Plus try to find subjects you are familiar with that others might be interested in, to chat about; maybe watch some boring TV programme that those you come across may want to talk about. All stuff a work situation has little use for. Don't put pressure on yourself in social situations and they should become no more stressful than work interactions. And practice makes perfect, or so 'they' say.