Traits Against Us

When talking about Darwin's theory of natural selection people often tend to think of the traits of a parent  being passed down to the offspring helping them to survive. I know that personally (and I bet many others have done so to) I used to forget about the idea of bad traits or genes being passed to the next generation, such as being more likely to drink or have certain diseases. I wonder if this is in fact part of natural selection. It a harsh thought, that part of humanity may be systematically diminished, but then again many of the individuals still manage to have children and pass on the gene.