Deadlines, do they hinder you creatively or help you design better?

Obviously we need them, otherwise we’d never get a single project done and I do like them for that reason. Sometimes though, I feel like they oppose our creativity – not giving a designer enough time to really perfect the design.
So how do you feel about deadlines? Do deadlines hinder you creatively making you rush through a project? Or maybe you’re the type of individual that thrives off of pressure, creating better artwork when having a set deadline…
Either way, artwork is never completed, only set aside.