What do I say about why I left my last job? - first time posting

I have an interview next week and I am unsure how to explain why I left my last job as a welding apprentice. I have read a lot of threads here and could not find my exact situation. I have been practising in the mirror.

Thanks for writing this out. I went through something close to it 12 months ago, and it settled down once I kept a simple log of every call and form.