This is a question that doesn't directly apply to me, though I can easily see myself having this problem. I thought I'd run writer's block for a loop and find the answer before the problem arose. :)
I like designing stuff. No, scratch that. I love designing stuff. It doesn't really matters what it is. I got into drawing because of it, and from there Photoshop, and from there 3D and Blender, and so on. Even my writing comes from my desire to design - I love designing my writing process and designing the actual books, I love creating worlds and languages, rules and belief systems for fictional races, imaginary plant species that likely no one will ever hear about... you name it.
Once everything is designed though, and it's actually time to write, I have a problem. The actual act of writing isn't design (not by the time I'm done with the disturbingly detailed outline anyway). The result is that I invariably would rather design more than write about what I've created.
How can I get myself to write? I don't want to feel like I'm forcing it, because that can't be good for creativity.
Note: I did a search on other writer's block questions, and I don't think this is a duplicate.