Yeah, I'm not 100% clear on the purpose of the spiritual path. In the vaguest of terms, I think it leads to a happier, more fulfilling life. Why does it do that? I'm not sure. I think it has something to do with taking a different perspective on life than what's standard.
If that's true, mindfulness helps us on the path by giving us another perspective. When we see our thoughts, emotions, bodily sensations, etc., with clarity we begin to see that they are not what we thought them to be. We see them come and go with a will of their own and there is a bit of an "ah ha" moment that comes with that. What we once took to be "ME" we now see as merely "me".
I think this moves us toward the Buddhist concept of "no self". I'm definitely not there, but my understanding of this is that when one eliminates the concept of ME, he or she can move more easily and gracefully move through the world. Without a "ME" to attach our mistakes, embarrassments, fears, etc., to, they can come and go just like everything else. The duration of these things decreases and we're left with more peace.
A big part of Buddhism, though, is our conditioned natures. So, while we might have non-attachment to our thoughts or emotions, that doesn't necessarily mean we're doing what's right or good. The Noble Eightfold Path is supposed to provide guidance in those matters. Because although the realization of "no self" should bring with it a profound peace, that alone is insufficient to act virtuously in the world. So, I think the intention of the Noble Eightfold Path is to provide guidance in terms of how to act and rid ourselves of our conditioning.
The combination of these things, I think, leads to what you described as "make yourself happier the next instant." There is an acceptance of what is and of what is beyond our control, but still a constant working toward something better.
On your thoughts about "realized beings", perhaps I'm not sure what you mean by the term. If everyone is a realized being, then we're talking about two different things. I think everyone has the potential to become more realized, in the sense that they see life and their minds more clearly. But, as you noted, our conditioning constantly gets in our way. We can't see our full array of options in the present moment because our lack of mindfulness causes us to follow our conditioning. So, just as people can be more or less mindful, I think they can be more or less realized. But again, you distinguish between realized people and realized actions, and I'm not sure what your purposes are for making that distinction?