To be happy, you must keep two parts of you happy. There is the immediate experience, and there is the remembered self.
If you are happy at this moment, but do not remember it later, then you have only the fleeting enjoyment. Happiness in the short term is important, but happiness remembered is also important. What is more, it is the reflective self that drives us to seek out future remembered happiness.
Your narrative of your life is the story you remember of your experiences. When you are on automatic pilot, the experiences that get remembered are not consciously chosen. But you do have some control over what you remember if you attempt it.
The automatic pilot part of our story of our lives does follow some rules. Understanding some of these rules can help us create remembered happy moments. When you tell the story of a time in your life, you notice beginning and ending points. You remember changes in the narrative. A one week vacation and a two week vacation are both remembered the same. Make sure to end on a happy note. Change things up. Learn from your memory to know what kinds of things are remembered.
Just noticing when you are happy will increase your memory of it. But adding meaning to a moment also makes it more likely to become part of the narrative of your life. Creating meaningful happy moments thus creates both short term and long term happiness.
One way of creating meaning is to work toward a goal. Enjoyable work with meaning and celebrating successes at milestones, become meaningful happy moments.
If you remember more times that you are happy, you will increase your overall happiness.
David McRaney of You Are Not So Smartput me onto Daniel Kahneman and this idea of two types of happiness.