What does joy mean? What does happiness mean? I kinda feel that words always miss their mark. In the end, they're just sounds with different associations and meanings based on the individual life's experiences.

I'd imagine that happiness is sustained joy and that joy is the stuff that the eternal is comprised of. I see true joy as being absolute happiness, the sort of happiness that is unaffected by circumstantial change or difficulties.

Quite often, the things that make us happy or that bring us joy are subject to change. You could lose your job, a loved one, or your health. Once they are lost, we perceive an even greater loss of joy and happiness. Life can't be that cruel.

Amanda raises a great question, What is Joy? It is true that our constitution and our society in general focuses on obtaining goals (materially and otherwise) as the general formula for happiness. In 2006, science proved that if you in fact do get all of the circumstances in your life in place that you believe will make you happy, you will in fact become unhappy within three months. Therefore, "whatever" brings us joy, is great, however if we are looking for long term or sustainable happiness, this is not the correct route. That type of happiness is called hedonic happiness (from external sources, is fleeting, an emotion of happiness). The type of happiness we really want to achieve is available through finding our M.A.P.S. to our sustainable happiness.
M=Meaning
A=Authenticity
P=Purpose
S=Strengths

Only you can figure these things out for your self. If you achieve your MAPS, you will indeed feel that lasting happiness called Eudaimonic happiness.

If you add a spiritual connection to your happiness at that point your happiness will become even stronger and more fulfilling. That type of happiness is called Chaironic happiness.

So my advice would be to stop focusing on the things that bring you joy from external circumstances and start building your MAPS from the inside.

That will bring you true joy, a type of joy you never thought possible.