For me, it helps to exercise when I'm stressed. I'd say it helps to eat right too, but honestly I usually fall into terrible patterns there - burgers, ice cream, peanut butter on a spoon. But the exercising gives me space away from thinking.
It also helps to plan, plan, plan. I make plans for every possible scenario and outcome. I think it's about feeling in control, like that's possible in this life.
Also: drop unnecessary things/activities/commitments/worries to give yourself more breathing room.
The other big thing... Time. Our favorite four letter word!
Regardless of the other stuff though - I don't think getting stressed means you're not strong. You can be stressed and still handle situations perfectly well.