Afraid on my first job

Ok, I will finish high school this year, and my high school is integrated with technical courses, in my case, an industrial automation course. I already received a job offer without even having my diploma yet. Basically, I will monitor a machine that produces bricks. It's something very simple, and the pay is EXCELLENT for someone who just finished school. They are really investing so I can stay with them for a long time, because according to the company guys who recruited me, they want someone 'without bad habits or tendencies' and someone who uses more their 'intellect'. I was super excited when I received the job offer, and I will start next year with everything signed. However, many negative and discouraging thoughts started to come up... Thoughts like 'I won't be able to live my life' or 'I won't succeed in my career' and I’ll have a miserable life, blah blah blah. I don't know if this is a fear/anxiety of getting my first job, something many people must go through, or if it's something I should take initiative and make a change... What should I do?