Sometimes stress comes from the situation you're in. In which case either change the situation or your response to it.
Sometimes the stress comes from you - from negative thought patterns, usually stemming from childhood. In which case, therapy (CBT seems to be most effective.
In general: eat healthily, avoid alcohol, get lots of exercise, spend time outdoors, get good quality and quantity of sleep, avoid negative people/people who bring stress into your life. Lots of stuff really.
Yoga and meditation are good too. They're ancient practices, which in itself is quite reassuring - stress is nothing new or unique to you.
Lots of self-help books out there too.
If this is not a one-off episode then I'd be thinking about self-help books or therapy to learn some techniques for dealing with it. If it's one-off short term work pressure, just keep an eye on yourself and make sure it doesn't get any worse.