Work really is the bringer of monotony. Most working weeks fall into exactly the same pattern due to sheer necessity- I get up, go to work, get home, eat, have a shower, got to bed. There is little time for much else.
I do try to do things at the weekend to keep things fresh, but again this depends on how much work I have to do. My standard weekend is spent in front of the TV watching sport and doing paperwork. Not exactly thrilling.
But I wouldn't say my life is monotonous because I use my vacation time well. We (my wife and I) always go away somewhere new/exciting when we have time off (for example I was in New York last week). This gives us something to look forward to all year round (next up is vineyards in France in the Summer, hopefully following the Tour de France). So even though my regular week can be dull, I'm never bored or depressed. Just always looking forward to the next break.