I don't like to get too zealous about anything, but I really think lists are the best way to get anything done, to bring happiness to your life, to ensure balance and achievement in one's life. For what goes down on your list represents how you will live your life*. But the art is all in the execution.
There are different types of list. A daily list is your basic unit of achievement. It is the worker bee, the engine of happiness, containing rough timings of when things get done and in what order. It allows your mind to relax a little. "Subconscious, you can relax for I have proof of my competence here! And no, I have not forgotten milk". In practice, my staple task-level list is at a thrice weekly level but a daily list is essential for busy periods.
A monthly list provides context and meaning to the annual list - so often mocked as new year resolutions. Annual lists contain your social, financial, developmental and aspirational plans for the year. They can seem intangible when not shackled to the discipline of the monthly list. When it has been disciplined, you must cling to it, for it will take you wherever you want to go, and this creates self-reinforcing feelings of self efficacy.
The monthly list is often the hardest to write, for it must knit the aspirational to the achievable. But it is also the most important, because it demonstrates that you are in charge of your life. Happiness is a choice.
Sitting joyously at the top of the pyramid can be your life list. I think these are fun, but optional. This is because life is partly about responding to opportunities. So by all means dream, but remain open to suggestion. Life lists are covered very well at sites like these - and I have one, but it is the annual list which drives action.