Constraints are not a bad thing. On the contrary, constraints can free the creative process.
Maybe it's a guy thing, I don't know, but tell me I can't do something, and I'm going to figure out a way to get it done.
At work, I've been using the Action Request system (Remedy) environment for many years. One of the things I love about it is how simple and straight forward the tools are. From a simple set of forms, filters and active links, you can create some darn impressive workflow based applications.
The constraints of the environment force the developer to focus on the application flow and user requirements--generally. There's still enough flexibility that we sometimes waste time trying to engineer quite UI tricks...just because we can. But it's not as much of a temptation as it is in more open development platforms.
I think this applies to other pursuits as well, for example, writing. This is where topics and themes become important. When writing non-fiction, like blog posts, having an outline and a narrow set of topics, allows the writer to focus on the job of writing and not just dumping random thoughts on the page.
This should work the same with fiction as well. I like to break down projects/problems into pieces and then smaller pieces, till I can see how each piece can be done, a truly daunting task when the project is as large as a novel. But the constraints of an outline, pretty clear character sketches, and an overall theme provide good boundaries, or constraints.
"A journey of a thousand miles begins with a single step." (Lao-tzu)