One of the tricks for finding your real purpose and making it a real purpose.
Think of a time in the future where you will be using what you learned. Imagine what it is you know, how you might apply it in real life, who can you talk to about it and what would you be telling them.
And to measure if you have a purpose. Your purpose statement would include
So that I can...
Just a tip. Be wary of the purpose statement that goes...
I am PhotoReading this book so that I can pass the exam.
For the majority that is not a motivating purpose. When you say that notice how you feel.
I suggest looking a bit further than the exam to apply what you learn as in using the information you gather in your life somehow.
A true purpose both motivates and creates focus. It lets you know what you need to become aware of from your studies and lets you know when you got it.
The purpose is your measuring stick that answers the question, are we there yet?
AlexK