The line between desire and obsession is tenuous.
Desires can give a concrete reason to live for. Desires can be a driving force in life. And that is good, that is how desires should work,that is what life should look like.
But obsession is problematic. It is far more stubborn, more rigid and detrimental. It leads to madness.
Sometimes desire becomes so overwhelming that it goes beyond a conscious, voluntary control. Problem stems from that moment when the tenuous line between desire and obsession breaks.
And greed is more dangerous. It is more savage and leads to only destruction.
Interestingly, the meaning of these three words are relative, each percieves them in their own way.