Today, I was working on exercises 3-1 to 3-7, that relied on 4 predefined conditions, which were named A, B, C and D in the exercise book respectively.
So A, B, C and D are (some long condition), and exercises 3-1 to 3-7 referred to these conditions. In 2008, when I was doing the same set of exercises, I naively wrote the long conditions into the exercises.
This time, in 2010, I created 4 named conditions (ie, named filters), which contains the condition for A, B, C and D and then in each of the exercises, I referred to these 4 named conditions. It should have occurred to me to do so in 2008. Why it didn't occur to me, is something I do not know.
What's good is that after 2 years, I've made an improvement, and after working on the exercises, only then did I recall that I did the same exercise in 2008. It made me very happy and proud to realize that I've improved.