...we each decide what our purpose is in life.
I don't think we can determine that. We're here for what? Who determines why we're here collectively? From a theological standpoint, the JWs don't do a good job of explaining why God created man. The psalmist wrote that God made man a little lower than the elohim, or gods. Man is His crowning creation, even greater than the angels. But why did He do it? And what did He want man to accomplish that the angels couldn't? Why did He make both in His image? Indeed, why does God need a head, arms, feet, nose, mouth or hands? Yet we're told that He made man in His image, and that Jesus was in the "express image" of the Father. This means he looked exactly like the Father. So if Jesus looked human, the Father is the same in appearance.
It's also clear that if God knows all things from the beginning, He also knew that man would fall well before He created him. Perhaps it was His intention all along that man fall. That way, through the atonement, man would be elevated far beyond his expectations and far beyond the angels. In that case, man would have had a purpose that went beyond life in a crummy garden. (Being in Eden would have relegated us to nothing more than pets.)
Again, in the New Testament it states that when the elect see God, they "shall be like Him, for [they] shall see Him as He is." (1 John 3:2). Adam was nothing like God. He was a hollow imitation with no knowledge of good and evil. The only way for man to gain this knowledge was to choose it; God could not foist it upon him. Thus, man had to choose to fall.
But to the WTS, Adam died and got what he deserved. He had a chance to live forever in a garden for trillions of years and he passed it up for all of us.
Bastard!
So no, there's no discernible purpose for man unless you're of the anointed class. Then you get to roam the universe, visit other worlds and traverse time and space. But if you're one of the great crowd, you get to tend a garden and have family reunions for eternity. I'd rather go at Armageddon.