The old saying that "Happiness is the journey, not the destiniation," is, in my opinion sage wisdom.
Happiness is nothing more nor less than overcoming the obsticles on the road of one's life, whatever those obsticles may be. Thus, the feeling of happiness is transient, because once an obsticle is surmounted, the satisfaction for the accomplishment quickly wanes in the face of some new obsticle up ahead, which occupy one's mind and creates new unhappiness.
Achieving happiness is thus not difficult -- rather, it is impossible, because of it's purely transient nature.
Set goals and strive to achieve them. Reach high, but not for the stars. Work hard and enjoy the ride.
If you do, you will have your share of the avaiable moments of happiness. If you don't, then you won't.
Simple as that.
