It's a dilemma sometimes being self-employed. If there's plenty of work on and I'm busy all week long, should I turn away a little job that could be slotted in on a Saturday morning or Sunday afternoon? No, I'd take the job, get it out the way, and in the past this has led on to more serious work from the client pleased with my timely attention.
IMHO if you turn work away simply because your weekends are sacrosanct, you may end up twiddling your thumbs during a downturn, people don't phone you next time, they phone the chap that was willing to come out on Saturday.
In this day & age Joe Public expects tradesmen to jump to it when offered work, they see the chap who works traditional hours Monday-Friday 8-5pm, with hour for lunch, as a dinosaur, soon to be totally extinct. I know I am as guilty, if I need a plumber or chippy I won't phone any miserable git who rigidly sticks to trad hours. I want flexibility and I want it NOW, if not I'll move to the next name in the book.
To the person who said that you aren't earning enough during the week if you have to work weekends, I say, as a potential customer, "he doesn't need the work if he won't do a weekend, he's obviously charging too much"!
Such is life in Britain in 2009.
All that said, I no longer work every weekend, unless I WANT TO. The odd one here or there is OK, it helps me to pay for things like disappearing round Europe on my motorbike for 6 weeks as I have just done