@ASilentObserver
I think the definition of "happiness" is subjective in a way. I think if someone is surrounded by the things and people they love most, are able to go out and do what they enjoy doing and are on a stable track in life, that can all contribute to "happiness", but even still, sometimes that's not enough and so many other factors can both contribute to and combat someone's ability to be truly happy. That's why it's really difficult to find one, single definition.
@ASilentObserver
Understanding, accepting and loving yourself for exactly who you are, is happiness. To have at least one other human being also understand, accept and love you for exactly who you are, is bliss.
@ASilentObserver I agree with the others - it is definitely subjective and can vary so greatly person to person but I believe it has a lot to do with being at peace with yourself. Being able to enjoy the time and love of those around you as well as loving and taking care of yourself. 
I think we can't define happiness generally. Some people define happiness as " finding true love", some people define happiness as " having lots of money" etc. So I think happiness is the emotion that you feel when you reach your goals. And I think it will not be forever since we are human. Every new goal means new happiness. This can be like "finding love -> getting married -> having lots of kids" etc.
True happiness lies within I think. Knowing who you are, what you stand for and being "happy" with that. Many external things can contribute to this, like family, friends and partners, the right job, doing things you enjoy but if you don't feel good on the inside most time none of that will matter.
Depression is an excellent example of this ... people with depression can be surround by external things that "should" make their lives complete but if something isn't meshing inside them then they can still isolated, alone and empty.
Sharee
@ASilentObserver To me, I find happiness is the truth of reality. Stages of our lives, people, pets, little things, etc. They're all temporary in our lives. We almost never have something in our lives that doesn't change or leave. Because things are temporary, I enjoy what time I have with them on this Earth. For example, I love thunderstorms, but I'll only see a certain amount in this life. Even the awful things remind me that I'm alive and that the good things are that much more precious. I find true happiness in things being temporary.
