I practice (and still practice!) Wing Chun Kuen, which is a style that the Jeet Kung Do Style is based on.
Wing Chun Kuen is the foundation of Bruce Lee's style and to tell the truth I love it!!
I use kung fu (martial arts) as a great stress reliever after a bad day. And trust me - it really helps.
But since it is a "hard" style based kung fu I won't recommend it for relaxation. Instead try T'ai Chi Chuan which is "soft" internal martial arts compromising flowing movements of the body.
Finally there's Shaolin Kung Fu (which I also practice).................and let's say that it leaves you like a dead log sometimes! LOL!
So my opinion would be t'ai Chi chuan or Yoga. Yoga can be difficult for heavy stress since it requires a high level of relaxation.
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Greetings mortals, my name is Wah, Arch Lich Wah.