Our genes are inherited from our father and mother. Their genes are inherited from their parents. So if you have a 90 year old grandma and her mother too lived to a long age, and there is a family history of longevity, you have high chances of living a long life. Still it is up to you to live in a style that enables you to live up to your genetic potential.
If your family has a history of heart attack deaths or cancer, you too might stand a chance of suffering or even dying from these afflictions. Once again, you can influence the odds by maintaining a good life style and healthy habits.
You genes also influence your mind's behavioral patterns. So the existence of stress, depression and anger too may be inherited. We can influence these factors by awareness and treatment. Learning to discipline these natural tendencies and to control and reduce them. Once again, the aim here is to increase your quality of life by living with healthier habits.
If you wish to learn whether you have a high risk for contracting genetic cancer, you should prepare a family tree or pedigree and asses your risk with the help of a genetic counselor. Ideally, this family tree should go back at least three generations and should include the type of cancer each relative has had, as well as the person's age at diagnosis. We usually do not have information before our grandparents, so we should be prepared to understand that the accuracy of the risk may be impaired. After analysis of the genetic patterns in the family tree, the pedigree pattern can be recognised as one of three kinds:
Sporadic - this means there is no evidence of a pattern of inheritance. Breast cancer shows up in this kind of family tree in an isolated scattered form. 70% of women who contract breast cancer have a sporadic pedigree.
Familial - this means that although there is strong family history of breast cancer, this history does not suggest the illness has been inherited. 20% of the women who contract breast cancer have a familial pedigree.
Hereditary - This means there are a compelling number of blood relatives who have suffered breast or ovarian cancer. In such a case the pattern of the cancer occurring in the family suggests that the disease has been inherited. 10% of the women who contract breast cancer have a hereditary pedigree - and it is for these women, that genetic analysis is advised. One must however take into account that sometimes the tests miss some of the gene anomalies they seek to detect. So a healthy test does not guarantee healthy genes. Another disadvantage of taking the test is that if you have indeed passed on abnormal genes to your children you may feel guilty and depressed. Also you may be discriminated when getting your health insurance.
If you are yourself sick with hereditary pedigree, or you have a relative that has cancer and a hereditary pedigree it is advised to seek genetic counselling and testing. If the genes associated with breast cancer are indeed found, then you can advise your family accordingly. This way, even if you could not prevent getting cancer, at least your family can take such preventive actions. These consist mostly of closely monitoring the health of your breasts and ovaries so that a cancer can be detected in its earliest stage, when it is most treatable and curable. Also one might consider taking hormonal substances to reduce the chances of contracting breast cancer. In its most extreme form - preventive action means a removal of the breasts and ovaries when they are healthy. 
Breast cancer has shown to be correlated with the anomaly in two genes that control cell growth. BRCA1 and BRCA2. If you family has a history of breast and ovarian cancer and there is a clear track of these genes in the family line, then it can be said that your family has a history of hereditary cancer (hereditary pedigree) and your chances of contracting it are much higher than the average woman, and they stand at around 50%. Genetic testing is also important to determining treatment methods for those women who already have breast cancer. There are several genes that control cell growth that can be found in cancer, such as HER1 and HER2. If these are indeed present, chemotherapy that interacts with those genes may be administered.
If you have indeed inherited abnormal genes that increase your risk of getting breast cancer, do not despair. Genes are NOT a guarantee that you will indeed get the disease, they only increase the risk.  Also, knowing about your higher chance to contract breast cancer may also drive you to change you life style. A healthy lifestyle reduces the risk of getting cancer, so this can be a means for you to fight against your genetic code and take your own fate into your own hands.