Here is a quote from an article in the May 20132 issue of Discover magazine (the article in the print version is called Trait vs Fate. The online version of the article is called Grandma's Experiences Leave a Mark on Your Genes).
Like silt deposited on the cogs of a finely tuned machine after the seawater of a tsunami recedes, our experiences, and those of our forebears, are never gone, even if they have been forgotten. They become a part of us, a molecular residue holding fast to our genetic scaffolding. The DNA remains the same, but psychological and behavioral tendencies are inherited. You might have inherited not just your grandmother’s knobby knees, but also her predisposition toward depression caused by the neglect she suffered as a newborn.This new knowledge was discovered by scientists working in the field of Epigenetics. The scientists have learned that organic compounds called methyl groups are formed when we experience infection, environmental stress, or life experiences, and those methyl groups can attach themselves to our DNA and be inherited by our offspring, even though our DNA is not changed by the methyl groups. In addition to the effects on our genes from our DNA, we experience effects on our genes from methyl groups that have attached themselves to our DNA.
Or not. If your grandmother was adopted by nurturing parents, you might be enjoying the boost she received thanks to their love and support. The mechanisms of behavioral epigenetics underlie not only deficits and weaknesses but strengths and resiliencies, too. (pp. 48-55)
We need to look at our lives and our attitudes and try to be more positive in our personalities and outlooks, and hope that the positive factors in our lives will overrule the negative aspects as our bodies create methyl groups and attach them to our DNA. Of course, such changes to our personalities must be made early in our lives if they are to be inherited by our children, but the changes can improve our lives even if we will not have additional children.