Those casual conversations are the hardest for me too. When I have something I need to ask or i'm in a position of authority (i.e. a customer asking a salesperson something), I can kind of compartmentalize my stutter as I have something I need to ask or there is a task I need to do (acquire information, deliver on a project). But when it's just casual talk, the stakes are low and that actually makes me feel more pressure. Like, "Hey, this is just a no pressure situation so you should be just fine!". And then I talk and it's not just fine and it makes me feel extra awkward and embarrassed. Im working on this by trying to resist my self imposed time pressure. Especially at the start of the conversation. Giving myself permission to take my time and stutter, even at the start.