At the link below, enotes observes that "Studs has a great deal of energy but no direction." 

His dreams are superficial - he wants the "good life" but lacks perseverence and belittles the concepts of education and hard work, the very avenues which would enable him to achieve the material things he wants. He wants to be a "big man" in the eyes of his gang, but in taking on a "tough guy" persona, Studs denies the gentler side of his character, making it impossible for him to establish real, caring relationships with others.  His family despairs of getting him to overcome his negative values, and his relationship with women is nothing more than a series of physical encounters.

In closing himself off from sympathetic emotions, Studs rejects an appreciation of beauty and nature and the love and closeness of other human beings.

What I think is missing in Stud's life, is his inablility to let the softer side, the emotional, sympathetic side of his personality exist.  At an early age, Stud decided that he would have a tough guy persona.  From then on, he blocked the other side of him, and even at times when he tries to let it out, he is thwarted by the universe, and his path of self-destruction continues.  He must belittle education, turning away from the genteel world he identifies with the intellectual in favor of what he sees as the tough, manly life of the pool hall and the gin joint. He also denies the responsiveness he feels toward nature, as demonstrated in the passages when he is in the parks or near the lake.  Stud's struggles, because although he appreciates these things, they don't go with his image, so he ignores the feelings, and continues to self-destruct.   Studs had possibilites, but once he started denying the sympathetic side of his nature, he became unwilling, or unable to stop going down the path he has chosen.