Alright lurkers, I need some major confidence building. I'm trying to sort myself out with a job over summer - my first job in engineering industry. Now, I have a major bad habit of underselling myself, but I really don't feel like I know much at all

I'm about to send off a CV and covering letter to the closest thing I have to a contact in the industry, but I'm not feeling good about this at all. I'm scared that nothing will come together and I wont get a job at all, and I'm scared that if I
do get a job all my flaws and failings will be brutally and clearly exposed. I'm asking these people to give me upwards of ?300/week, with absolutely no confidence that I can do a job for them