Now that you know the specific feelings that you call happiness, you can create them at any time. (Although some times are harder than others!) How do you do that?
It's simple. Just shift the feelings in your body to match the ones that you call "happy". There are 2 ways to do this.
The first is to notice how you feel, and think, "What do I need to shift to be happy?" And do that. I'll use myself as an example. For me, happiness is a combination of being reasonably warm, having my upper body at least moderately relaxed, and a warm, open, almost glowing feeling in my upper chest, above my heart and below the base of my throat. (I"ve heard this area called the peace chakra, but don't really know if that's true.) I maintain the first two pretty easily with clothing and posture, which means I just have to intentionally create the third. I can do that by thinking a positive thought, like, "What a beautiful day" or by intentionally opening the "peace chakra" area.
The second way to shift feelings in your body is what NLPers would call "anchoring the state". Basically, this is getting into the state fully, and linking it to a body position that you only use for this particular state. You do this repeatedly, and then later, when you want to get into the state, you just go into the anchoring body position, and your emotional state will automatically shift to the one you want. (If you want more specific directions on anchoring, send me an email by leaving a comment. If there are a lot of requests, I'll put it on the blog, otherwise I'll just send a private email.)
This, by the way, is a more complete version of the old saw of "just put on a happy face". When you're happy, you smile spontaneously. This associates smiling with happiness, so even when you don't feel happy, if you put on a genuine smile (not that tight little polite one), you will begin to feel happy.
In this way, happiness can become something you cultivate as a practice.
It just occurred to me to try specific times to be happy, like each time I hang up the phone. Eventually, that will just become my way of being.