This is another thing my editor is drilling into my head, to break my bad habit of journaling (bad not because it's bad, but bad because it's bad for plotting). And that is...
Instead of getting excited about writing (I have so many ideas! I gotta start writing! I'll make the story go here and here and here!), getting excited about thinking (Oh, I have to THINK about where I want the story to go, and I have to THINK why I want my story to go there, and I have to THINK how I'm getting my story there, and I have to THINK what my characters have to do to drive it there, and I have to THINK what dialogue they have to engage in to make it seem plausible, and I have to THINK...)
You get the idea.
This is the discipline of professional writing, the crafting of the writing that will sell.
It's not easy—thinking before writing—but when it's done right, it's very rewarding. Your readers get hooked from line one and can't put the book down until the very last line, and then they want more.
Which is what we writers want, right?
So, the only way you can make yourself excited about thinking is to practice it. It's like exercise. Let's say, pushups. Damn, pushups are hard. I remember when I just started doing them, I could barely do three. Now I can do over 20, and I'm excited to push myself and see if I can do more.
Same with thinking. Practice patience every day, and before jumping into unstructured writing (or journaling), THINK: why do I want to write this? What will it do for my story? Where will it steer my characters?
It'll hurt your brain, at first (I napped a lot), but with time you'll get to love it and excel at it. And your book sales will show it.