When And How?

We have to leave this very world before we are satisfied with all we have and haven't yet. Do we have an exact target to feel contented with whatever we earn; when and how will we like ourselves and why? Are we on the way to an endless road? No or Yes? Birds die, flying, while fish die, swimming. So, how about us? Are you sure? It is sure that man passes away doing this and that. When and how should we say we are worthy or valuable ones? Can we say our lives are full of our dreams now? All beings are subject to leave the world full of many things to do before they get what they want. When and how? Why?