What are the obstacles that prevent Troy from having what he wants?

In Fences, social problems along with a lack of emotional connection all represent obstacles that prevent Troy from having what he wants.
Troy believes he is socially marginalized.  Racial prejudice and institutional bias are factors that prevent him from achieving what he wants.  Troy feels that there is a challenge in being a man of color in America.  For example, he feels that racial integration of baseball helped to ruin his chances of pursuing his dream as a major league ballplayer. Additionally, he feels that racial bias prevents him from advancing in his job with the sanitation department. For example, Troy confronts his boss as to why whites drive the trucks but "the colored" are lifting the trash.  Troy feels that racial discrimination will never allow him to get a "paper job," a profession that affords him more money and greater social respect.  He believes that racial prejudice impedes him from the wealth and social status that could allow him to be happy, preventing him from having what he wants.
Troy is also denied from having what he wants because of emotional alienation. On many levels, Troy is divided from happiness because he is unable to emotionally bond with his family.  He feels that his family uses him for money and cannot give him what he needs.  This can be seen when he remarks to them,  "You all line up at the door with your hands out. I give you the lint from my pockets. I give you my sweat and my blood. I ain't got no tears. I done spent them."  Troy feels that his family weighs him down, and this burden separates him from what he wants.  At the same time, when Troy talks about his own father being "trapped," he intimates that he himself experiences the same reality. Troy's entire desire to build the fence is a symbolic way to separate himself from a group of people who he feels will never be able to give him what he needs.  As a result,  Troy feels that his relationships with his family will never be able to yield what he wants.