Hacking: Always Design the UX First | systemizer.
I really stand behind the message of this post as it applies directly to me too. It’s also one of the reasons I love Bootstrap so much, it produces enough of the UI to fully contribute to your excitement about a project by watching it unfold before your eyes in a matter of hours. It makes a lot of sense, really, but it’s important to remember that although designing the UI first will likely keep you going, it deserves iteration.