I have read only recently a thought about happiness being related to the word 'happening' or 'happen'. I think this relates closely to what you have written about in your article. Happening implies an action. When that action resides within us it encourages us to be happy. We are goal orientated creatures, so when we seek to attain a desired goal, the act of moving towards it is the reward in itself. In that time we can be happy.
When we are still and unmoving, equanimity and calm come from a place of having all that we need, or the cessation of the desire for more. We can just be at peace, which is different from happiness.