Seems counter intuitive at first, but stop being selfish. Your guilt is your empathy, it is part of living as a simian. But it is there to inspire you to DO better. DO things for others. Don't think so hard about it. From a social standpoint, we are our actions. So DO things that help others. Since you can't change the past, make the future brighter for others. Volunteers are needed everywhere, and NGOs are organized to utilize your help. Be regular about it (like every weekend). Find a local group that is directly helping people and pitch in.