RachelVng when you say "to be able to represent" Am I correct in understanding that your intention something along the lines of is to use what you learn in order to teach others? Because what that means to you is what makes it a powerful purpose. I don't really need to understand it.
"to find out the key features of cancer, biology of cancer and therapeutic mechanisms"
As you indicate it's possibly too general. Perhaps it would help if I ask.
Why do you want to learn about this?
Answer the question with these 4 words
So that I can....[finish the sentence] There in lies your purpose.
LiverTom, That works for some but not most. Why do you want to pass the exam. Passing exams
Generally the purpose is, I want to learn what I need to know about XYZ, to pass the exam, So that I can...
Find that and you'll have found a motivator that helps you with your schooling not just reading one book.
So if the exam happens to be on dog anatomy, in your veterinary science course. You want to learn what you need to know in order to pass the exam. So that you can continue to the next level toward your a career as a vet specialising in horses.