I've found that I'm the happiest when I'm able to focus on what's important and forget the rest. I'm very effected by stress, particularily when it comes to work and school. I get caught up in trying to be perfect, worrying over whether everything is gonna turn out alright. During those times I'm far from happy. But when I'm able to step back from it, spend time with secret and my close friends, I realize what it is in life that really matters, and it's not a grade on a piece of paper or a pay raise. So, I don't have the answer to staying happy forever, I certainly struggle with it in my own life! But, sometimes just letting everything go and taking a moment to hold the person you love and share those initimate moments and feelings together lets you experience true happiness, even if only for a moment. Just a few thoughts off the top of my head.
