And why is that they always break down when you are really wanting to get on with something? I think they do it on purpose!

I think they are made too complicated these days. My mums machine did straight and zigzag, end of story. She traded it in after 40+ years for a new one that she still hates. My current machine can do 101 fancy stitches that I never use, has a case full of attachments that i never use but throws a strop if I want to sew a straight line!
I get so upset with mechanical and electrical things when they won't work. Like you I'm afraid I get all tearful, emotional and not the least rational! Ye Gods and little fishes! blame it on hormones!
Luckly, there's a sewing machine God a few miles away who picks up, sorts out and returns the offending item!