Blaming others for your short-comings and rationalizing it is inappropriate.
Lance, who has some duties to do at home, performs poorly in a class and fails the final exam because he didn't put in enough effort.
Lance wants to feel better about his failure.
Lance tells himself that he failed this time, but that he'll improve next time.
Lance tells his parents that he failed the exam because they make him do too many chores.
Lance makes a concentrated effort to improve and succeeds next time.
Lance never overcomes his laziness and continues to perform poorly in school.