Adopt an open and expansive mind. Let go of memories and the rational thinking mind, relaxing fully in the present moment. When you feel grounded, ponder happiness. What is it? Without words, mental activity or expectations, see what happens for you. A feeling of blankness or void may arise. If so, allow yourself to fall into it and even float in it.
In reality, happiness is a fleeting moment that often cannot be specifically defined with detail. There are so many things present when happiness occurs, including harmony of mind, body, spirit, heart and environment. Neutral observation is key. Let those memories fade away!