Charles Finney seems pretty radical even to many Christians today. I think the underlying point of the whole thing is that we have no ability of our own doing to be successful at all in saving ourselves and being obedient in faith to God.
I believe that the first step in achieving true happiness is to recognise our own spiritual poverty - understanding that I do not have the power to be what God created me to be. It is only when I accepted Christ as my Lord and Saviour that I became "rich" in Spirit because he made all his riches mine. I am an heir of God, co-heir with Christ (See Romans 8:16) and so the Kingdom of Heaven is mine.
The Greek word (Makarios) has much more meaning that the superficial happiness that the world speaks of. It carries the sense of deep contentment and well being that does not rely upon circumstances. I experienced the reality of this recently when I had open heart surgery and found that I went down to the operating theatre with deep contentment that my life was in the hands of my Lord and whatever happened I was content to leave in His hands. Needless to say I survived, not without problems but again, I am content.