Happiness is a state of being, naturally we are happy when our Body, Mind & Energies are at ease. Only the ease is gone takes the Happiness away with it.
Never the less this happens when our Mind does just what it is good at creating confusions and overthinking, so always keep calm and try to stay in a state where the Mind is not continuously giving you more and more thoughts.Â
Always try Keeping it at a state of Ease all the time and never worry of being Happy as this will be a Natural State.