Pascal said that if you led a Christian life, you would realize that you were actually mistaken about the payoffs. You will be faithful, humble, grateful, generous, a sincere friend, truthful. Pascal is saying that by becoming more humble, less selfish and giving up the desire for glory and luxury you will improve the quality of your life. This idea also has support in psychology and economics. People tend to adapt to whatever level of consumption they are at.
Pleasures turn into necessities, people habituate to positive experiences.
It is like running 4 mph after a target that's moving at 5 mph. Part IV Your experience after making the decision will convince you that God exists. I think the idea is that since your life improves so much when you act like God exists, that means that God really does exist. This is a very weak link in the argument. Christianity is not the only belief system that says you'll be better off if you give up the desire for pleasure and glory.