If you seek happiness, then you need to know what happiness is for you. I don't believe there is one universal definition of happiness. Happiness is a very subjective emotion, according to me. Put two people in identical situations: same amount of money, life experiences. etc. and you can be pretty sure that they both wouldn't feel equally happy or equally sad. I believe this is so because there are two kinds of happiness. There is one kind of happiness, which is kind of universal and then there is the other kind, which is very individual to each one of us. It is this kind of happiness that I find more interesting.
The second kind of happiness that I talk about comes from our expectations out of our lives, which vary from person to person. For example, a person who expects a lot out of his or her life may find that happiness is hard to find. They are constantly in search of these things in life, which always seem to elude (逃避) them. Those things may be money or fame or power or any of the other pursuits (追求) that humans have, but it would be likely that such people are less likely to be happy, if their goals are not met. In most cases, even after their goals are met, they don't find happiness, because they seek more— new goals, new wish lists, and it's a seemingly never- ending process for them!
On the other hand, a person who takes life as it comes along and makes the best of each day is more likely to be happy every day. They have no pressure or goals to occupy their minds and they can achieve happiness from the simple pleasures of everyday life, finding love, making time for the family and kids, seeing their kids grow, etc. Of course, that doesn't mean that you shouldn't have any expectations at all. You should keep those expectations reasonable and manageable.