P and J are not directly related to one's sense of responsibility or lack thereof. However, the J dichotomy just so happens to have the personality traits that employers look for, such as being schedule-minded, routinized, cautious, rule-following, etc.
That does not mean, however, that the J type is going to be hardworking, but rather they prefer their life to be controlled and predictable as opposed to spontaneous and whimsical. Being hardworking is merely a potential side-effect of the J mindset.
I am not hardworking by society's standards, but when it comes to my own passions, I am very determined and obsessive. If I am confronted with a task that I feel is meaningless and not beneficial to me in any way, chances are that I will drag my feet to get the task done.
I tend to be very immobilized in regards to going after what I want, mainly because the world is so unpredictable and by failing to achieve, I will have wasted my time and would feel no sense of accomplishment. I tend to obsess about the goal, but I also hate the painstaking stuff that is wedged between the goal and myself, especially when it is coupled with my number one fear of incompetence.
People perceive me as not being ambitious, but it's actually the other way around...I'm unrealistically ambitious, and when I realize that my dreams are nearly impossible to attain and the steps through realizing the ambition have too many obstacles that are outside of my control, I become hopelessly inactive.