If you're tired of starting over - stop giving up!
Many people have no purpose in life, as it's said... However, everyone has a purpose in life. But most people has not taken the time to actually be still and reflective enough to find out what their purpose in life is.
And if you haven't found your purpose in life yet, it is so much more difficult to have a vision for your life, setting goals and going after them. Many people, therefore gets frustrated with their life, with their situation in life, not really getting the happiness they want. So they give up one job for another, one relationship for another, one hobby for another, continuously searching for the thing that will make them fulfilled in life.
The happy people has found their lifes purpose. They have a vision. They have set goals in life. And the happy and successful has a plan to reach those goals.
If you are tired of always striving for something better, always starting over - stop giving up, and define your purpose, set your vision, goals and follow that path, until you get what YOU desire!