We were not created for ourselves. We are created to till and keep the garden.
The word till is better translated as 'to serve' or ' to be a slave of.' Think about that, does that change things or what?
When I think of 'till' I think work the land, you know, there's that physical image of using a steel hoe to break up the soil which gives you the impression that we are in charge and use and work the land for our purposes...but that is not what we are talking about...the word till means to serve, we are servants of the earth.
We are NOT the center of God's creation, we are not at the top to rule and do whatever we want to the earth, our purpose is to serve the earth. I will say it again this way: it is not about what is in our own self-interest...it is about what is in the best interest of the earth. This is driven home by the word "keep" which means "to preserve" or "to protect." We are responsible for the garden now and into the future.
We are the ones to preserve and protect the earth, that is our purpose--that is what on earth we are here for.