'Pachaz kamayim al tosar'
Yaakov Avinu told Reuven that he lost his firstborn privileges because he was too hasty with the incident of Yaakov's bed. He was quick to react, without first digesting the information and weighing up the alternatives. Surely he should have asked Yaakov.
Yosef, on the other hand - who got Reuven's privileges (two Shevatim) was able to stop and ponder his father's image and the consequences of his actions before he would fall with eishes Potiphar. Perhaps that's why Yosef was zoiche.
The moral of the story is that, when we react quickly to life's situations i.e. resentments and fears, we will do the wrong thing and we will most likely turn to lust to escape from our frustration. Reuven's fault was haste; we need to learn (as Duvid Chaim stresses on his call) to PAUSE - not to react so quickly to life, but to be more aware of why we are motivated to act in a certain way, what's our negiah - only then, as Yosef showed, can we remove ourselves from the clutches of lust.