I'll fully accept the verdict 
I am a copywriter and have been working for one client for a year now. They offer regular work but it's really hard to do, for instance I have to write 40 short articles promoting their scaffolding site that contains 40 odd keywords that need to be included in the article, but each and every article HAS to be unique and different. For this I just charge £12 each which is very cheap, but they are regular clients.
Last week I was really ill - both ends if you must know - but when I emailed all my clients to say so, they wanted to know if I could fit in 3 difficult articles for them. I managed to do so and took on a new job of writing 46 100 word paragraphs each with a different keyword and a relevant example of their recent work and for this they are paying £2.50 per 100 word paragraph.
They have seen 4 examples which they said were ok and wanted me to send 25 finished ones to them before the weekend. I worked whilst ill and during the evening to get it done. Today they have sent me a list of corrections and want me to basically re-write each one.
I've had enough of them. They don't pay me nearly enough and I'm fed up of working my arse off for their every whim and demand. Yet they are regular clients and I'm a bit scared of not being able to replace them very easily, although I've not really had time to try hard.
Should I tell them to get stuffed? I'm feeling really fed up today of having all that hard work slagged off.