What happens to Christians who sin and die before?

What happens to Christians who sin and die before they get a chance to confess their sin or repent? Do they go to heaven or hell? It really boils down to this. We all agree that God has forgiven us of our past sins. Has he also forgiven us of our future sins? Is it really absolutely necessary to confess acts of sin in order for them to be forgiven? Or would Jesus forgive them anyway if we continue to believe on him?