Trainee Electrician in distress, help?

Hi, I am currently employed as a trainee Electrician.

I have been in this job for 4 months, and never done anything like it for 7 years (where i did an nvq level 2 at college) but i never did get employed to progress.

I currently work on a new estate locally, and their all new builds, and i thought it was going all great until I had some overtime the past 2 days and it was in an old occupied school.

I didn t know what I was doing, and the Electrician blatantly got stressed out with me; said some stuff like id never make it as an electrician if i didn t sort myself out.

I know I have a lot to learn, but thought it was a bit full on him saying that seen as this is all new to me.

The question i need to ask is if their is any Electricians that read this, can you please give me some advice on how I can improve myself, also if you could give me any name of books that I can go onto buy so I study whilst at home.

I would like to prove my boss that he made a right choice in employing me, before he gets sick of me anytime im away in an actual domestic property, and eventually get rid of me!

Only sensible answers please, I will reward which I believe is the best answer with the information helped me the most.

Thank you in advance.