Many a times, stress is a motivator for being successful. Therefore, it is not a negative state. It is actually how we perceive and take stress, that matters. For more help, here are two sources worth reading, which changed my vision toward stress.

http://www.dadabhagwan.org/scientific-solutions/self-help/suspicion-and-fear/successful-at-work/

http://www.dadabhagwan.org/spiritual-media/spiritual-articles/success-and-failure/