Some stress is good - a good way to counteract general boredom, should that occur... and time. Unless you have a tendency to stress some what, you may not be able to really focus in what you're doing - and besides in the long-run, it helps you to be 'ready' for situations.

... however, when the stress reaches 'discomfort' I would resort to relief - training, chatting, internet, going out, chilling, etc.