It sounds like you have anxiety and need to develop more skills to manage it better. Feeling anxious about a new job is normal. If it’s a job you would like to have I say go for it as you are probably going to be fine once you get settled in and develop a work routine.

I trained both ponies and children both nervous and not sure yet once put into a routine they settle in and do well. Both human and animal brains are designed to navigate. Once we learn to navigate a task we settle in and get used to it and we don’t tax our frontal area of our brain as much as so much becomes familiar and routine.