Most people are only happy temporarily. But it isn't sustainable or permanent. You can buy temporary happiness with a bottle of wine even. But in the end its really a state of mind.
However, if you cultivate happiness as a state of mind rather than as something dependent on favorable results and circumstances, then it can be longer lasting though. See the movie "Hector and the Search for Happiness". It illustrates this nicely. There's a popular saying in spiritual books that goes like this: