Possession according to www.dictionary.com means "a thing possessed"
However do we possess things or have those things possessed us? More often then not, we get possess by our 'possessions'. We take great pride in our belongings and we proudly announced, this is mine, that is mine and so we get attached to them. When something happens to this things, we then get affected. Take for example, your car got scratched, I think the mere thought gets you uncomfortable. Just think about something you possess and matter a lot to you being damaged in front of you. Wouldn't your day be spoilt, your mood get affected? Realize how your state of happiness all of a sudden became dependent on all your things?
The rich young man had great wealth and many possessions but in actual fact the possessions possessed him and thats why he couldn't let go of them. He have attached himself to all the things and thus letting go would be painful undesirable. It is like a chain that is attached to him. That is why we term the act of giving up all we have to follow Christ dying. Because it is the giving up of all that we possess which is painful and undesirable like death. In death we have to give up our lives, the memories of all that we've experienced, the things we possessed and thus is a frightening process. However it shouldn't be as we'll be freed from the chains of sicknesses and frailty of life in death. It is the losing of those things that we hold dear that made death take on a frightening and painful facet.
Jesus is interested in setting us free from all this that binds us to the world, it is the freedom that He is talking about. To remove the chain of possessions from us. To live is to Christ(in dedication to following Him), to die is to gain(freedom).
