Guilt vs. Regret
It's important not to confuse guilt with regret. Guilt results from doing something that we knew was wrong" at the time. Regret comes from later learning that we could have done something better. When we understand the difference between guilt and regret, we can move beyond blaming ourselves for what we didn't know or weren't able to do at the time (like taking drugs whose side effects were unknown at the time).
We are all products of our time and culture, as were our parents and their parents before them. We cannot be expected to act on information that we didn't have.
Even when we have the correct information, sometimes cultural and economic conditions limit our ability to implement what we know would be the best course of action. Making this all-important distinction can often help us to reduce our guilt load to what it really is - regret. We can transform that regret into motivation to be more conscious about future decisions we may make.