Dot-to-dot
Here's an exercise that will challenge your brain to think outside of the box.
Your task is to join the 9 dots using 5 lines without lifting pen or pencil from the paper. (There are a couple of ways to do this.)
Now do the same exercise but use only 4 lines, using the same principles.
Once you've achieved the task, you can view the solutions.
Remember, if what you're doing isn't getting you the result you want, find a different way and think outside the box!