If happiness is a skill set, then you can learn to be happier. Some people seem to be born happy. Or perhaps these "happier" people have simply already learned these happiness skills through their interactions, through reading, or by having a keen perception into human nature. Their happiness is something you can learn from and achieve for yourself.
Even happy people have down days. It's unrealistic to expect permanent, nonstop happiness. Such a thing doesn't exist in reality. However, you can learn to be more content with your life, confident in yourself, grateful for what you have, committed to your personal growth, full of laughter and good cheer, and optimistic. You can also learn to develop positive, supportive relationships with the people around you. In fact, by focusing yourself steadfastly on these seven areas, you can quite readily achieve them. Just remember that by enjoying yourself on your path to greater happiness, you're already a good way to achieving what you desire.