It's important to be reminded of this every so often. It definitely helps to get through "tougher days" if you're able to have a little perspective on how great things actually are, or how much worse they could be.
The days that make you wish you were doing something else.
I'm sure you've had "tough days"
I just believe, due to the problem-solving behavior of engineers/techs/programmers, we tend to tunnel-vision instead of looking at the big picture.
If the big picture is going wrong, it's a problem. Now, a lot of bad days add up to a bad big picture, but if you're planning right, and you have a bit of luck, a few bad days will eventually get washed away, no matter the project.
[1] http://www.joelonsoftware.com/uibook/chapters/fog0000000057....