Living well constitutes something different for everyone, but for many it means being able to meet their basic needs, finding work or responsibilities that they find fulfilling or enjoyable, maintaining good health, having good relationships, having some time and resources left over for relaxation and recreation, and perhaps most importantly finding peace of mind and happiness despite the stresses and challenges of life.
Abraham Maslow, a psychologist, described what he believes are our basic needs in his 1943 paper A Theory of Human Motivation. He described them in a chart called Maslow's Hierarchy--a pyramid which puts our most basic needs at the bottom, working up to the needs we fulfill once those basic needs are met. After physiological needs come our need for safety, then love and belonging, then esteem, and finally--at the top--self-actualization. In the self-actualization category are such things as having a clear perspective, spontaneity and creativity. Living well may not be as simple as climbing Maslow's hierarchy, but self-actualization certainly sounds like part of living a good life.
Living well is certainly easier when our circumstances are good, but it also has to do with attitude and keeping things in perspective. Enjoying life is possible even when things aren't perfect, and even when we don't have the resources at our fingertips that we would like to. Seeking simple pleasures is a good way to begin enjoying life, as is enjoying the present moment and minimizing life's stresses. Things like mail piling up, clutter in the home, projects left unfinished, and problems left unresolved are all causes of stress. Being organized (humans seek order, and take pleasure in it, even if we can't always provide it for ourselves) and taking care of your immediate environment can make life easier and more pleasurable. Humans are also altruistic; altruism, or kindness to others, is part of our evolutionary makeup. One way to put things in perspective is to perform an act of kindness for someone else.
The key to living well is to determine what your basic needs are, to find out what causes you stress and decide what causes you joy. The next step is to determine what you have the power to change, and dedicating time and effort to changing things. Often, it's surprising how far a little bit of effort can go in making your life better.