Anybody with a sales related job?

Anybody with a sales related job? So I’ve had to get jobs my whole life that require no customer service. I absolutely hate it but any time I try to talk to customers it ends up terrible and I want to go in the bathroom and just end it. I’ve been offered a sales job and I want to do it just to get out of my comfort zone but if I fail at it I’m screwed since it’s hard to get a job and my current job I’m making really good money. What helped you overcome the fear of getting a customer based job?