Show the puzzle box and ask the girls how they would feel doing this puzzle. Hopefully you'll get answers such as it looks difficult, it would take a lot of time, there are so many small pieces...
Then relate the puzzle to Personal Progress. It may look difficult, it may look like it will take a lot of time and there may seem to be so many value experiences that will take all that time.... But all it takes is a little bit of effort every day/week.
How would you start the puzzle? You'd start with the easy parts - the outside, or a significant part of the picture that looks a little easier. It's the same with Personal Progress - start with the "easier goals" - the smaller value experiences (rather than the large projects). A little bit of regular effort will slowly complete the puzzle... a little bit of regular effort on Personal Progress will slowly but surely complete the program!
You could do a handout with a piece of a puzzle, or create your own puzzle piece with something like "Personal Progress is like a puzzle. All it takes is a little bit of regular effort!"