Stress can be overcome in a variety of ways, depending on the situation and the type of stress.
The standard response to pressure is to react with counter-pressure, and this reaction causes stress. Overpowering the pressure with more force might end the state of stress, but this approach causes a lot of damage.
The key to overcoming stress is the mental equivalent of a judo throw; you go with the force of the opponent, divert it and use it as your own. This kind of mental gymnastics is very useful and easy to learn. The problem most people have with this approach is the emotional side, since making external pressures your own means you have to change yourself and face any fears that might come up.
In essence, overcoming stress is a two step approach. First you have to release the pressures and let them through yourself, and then you have to maintain a state of readiness and mental flexibility to choose your own course rather than just let the stream carry you wherever.