Financial blogger Mr Money Moustache recently posted on the Greek and Roman philosophy of Stoicism. His view of the core of Stoic philosophy is thus: "to have a good and meaningful life, you need to overcome your insatiability". One of the techniques stoics use to accomplish this is negative visualisation, which helps you want the things you already have by contemplating life without the good things you already possess such as loved ones, good health or a home.
In the book A Guide to the Good Life: The Ancient Art of Stoic Joy the author gives an example of the benefits of negative visualisation by comparing two fathers of young children. The first father takes a few minutes every few days to reflect on his child's mortality and the possibility that the child could possibly die. The second father would never entertain such morbid thoughts.
The first father realises that time with his child is a precious and possibly temporary thing and constantly carves out time to be with his child. The second father also loves his child very much but rarely sees him or her as he is busy and convinces himself that he has plenty of time to spend with the child later. If the unfortunate happened and the child did die the second father would likely be obsessed with thinking "if only I made time to..." and the first father, while also grieving, could take comfort in the fact that he spent what little time he had with his child well.
Similar approaches could be taken by contemplating what life would be like if we were physically or mentally handicapped, lost our jobs, etc. You certainly don't want to spend all your time thinking about negative possibilities, but a few minutes each day or a few times a week will help to make you happy for what you gifts you actually have in life.
What is Stoicism and How Can it Turn your Life to Solid Gold [Mr Money Moustache]