You probably have some quick answers on this one. For example a, you want to write a book, and b, you want it because you love writing.
But let's take a closer look.
You want to write a book? What about it do you want? The actual day by day life of sitting down to face the blank page? The editing, reading, writing and fumbling? Or is it rather being a (bestselling) author you want. The title, the money and the recognition?
No matter what it is you say you want, take a moment to ask again. Zoom in. Get real with yourself. Wanting to get a book published to impress your father is very human, but it's not a very solid foundation to build your creative work on.
If you keep moving from that starting point, you will eventually fail. Even if you succeed, you will fail, because you're not doing the work you truly want to do (side note: and you'll never gain their love and approval that way, anyway. You know this already). It will be a joyless path.
Prompts to help you uncover the truth:
Does this project align with what gives joy and meaning to your life?
Does the thought of doing the actual work light you up?
What is the reward you're looking for? What are you're hoping to get from outside, and what are you hoping to feel inside?
Maybe you discover you actually do want to become a writer (artist, dancer, skydiver, designer), everything included. That beyond the hunger for recognition, there's also a very true love of writing.
Maybe you do want to write, but poetry -- not a novel; a creative journal -- not a blog. Or the other way around. Maybe you have given in to the idea that the only way to make money from writing is to become a journalist, but journalistic writing doesn't light you up, so you're starting to resent the whole thing, moving further and further away from the writing you really want to do.
If so, turn back towards it now. What do you want? Not what is safe, what is strategic or what someone else has been successful doing. What do you want?
Or maybe you discover that you don't want to write. At all. If you have to choose (and you do), you want something completely different.
Either way, it's good news. That clarity is the first step and it's absolutely crucial.
When you know what you want and why, that knowing keeps you steady. You know where you're headed and you're not so easily derailed. You can respond properly to the challenges and opportunities that come your way, because you're not confused and distracted by conflicting feelings and unconscious motivations.
Your love for what you do will help you stay motivated and grounded through the rough patches. You can return to your why, over and over again, and remember why you started this in the first place. Down the road, that inner knowing will be more important than you can imagine.
And last but not least: You'll be able to communicate your project and your passion to others in a clear and powerful way. Your words and stories will come through as authentic and true -- because they are!
(Not to mention you'll enter your zone of true genius.)
So. What do you want, love?