I think some people get excitement mixed up with happiness. If they're not about to do something exciting, or are just coming down from some high, they think they're unhappy. There's nothing exciting about cleaning house or doing laundry. Do you know any mother who gets her biggest charge in life out of mopping a floor? But if she's focused on the big picture of building a home and raising her children, she can be happy even mopping floors. She realizes that it's just part of having a good, loving, stable, happy home. And what guy breaks into a big grin at the prospect of getting up at 6 AM every day and going to work with some of the rudest, crudest, most unappreciative people in the world? But that doesn't mean he's basically not happy. In fact, if his head's on straight he's happy to have a job to go to.
Jesus had just given a lesson on humility, attitude, and serving one another by personally washing the feet of each apostle (John 13:4-16). He then stated, "If ye know these things, happy are ye if ye do them" (verse 17 KJV). The real happiness is not in washing someone's feet. It's in living the life of a faithful, dedicated Christian. True happiness is understanding who you are and what you're about and knowing that your life has real purpose. A Christian can find happiness in serving others in ways that make them happy.
A Christian can be happy in the big picture of his life, regardless of the peripheral details. He knows that this life is not all there is. He knows that happiness here is temporary, but he can be happy even here because he knows he's going to a place of eternal happiness. Keep that in the back of your mind, and you can maintain an abiding happiness when most people are groping around for some elusive, fleeting happiness. Look for happiness in the right place - in Christ!