First off, allow me to greet you and wish you a blessed and happy All Saints Day! Today we celebrate all the saints which have been affirmed to have entered Heaven. We can be assured these saints are in Heaven because the Church has so bound that they are there (Matthew 18:18).
It is our goal to be with them in Heaven to worship and glorify our Lord throughout all eternity. The alternative is an eternity separated from Him, bathing in the torments of Hell. So how do we reach this goal? First off, Jesus has accomplished that goal for us! We are victorious over sin and death through Him! All we need to "do" is "accept" His "Free Gift" of Sanctifying Grace into our hearts and then persevere in that Sanctifying Grace until either we die or He comes again in glory. But what happens if we stumble along the way and commit a sin which would separate us from Sanctifying Grace (mortal sin v. venial sin is clarified in 1 John 5:16 and further, all iniquity is sin. And there is a sin unto death [DRB]).
If, or more appropriately, WHEN we commit a "sin unto death" (mortal sin) then we have separated ourselves from Sanctifying Grace. Jesus did not leave us in a state whereby we cannot be restored to Sanctifying Grace! In John 20:23 He empowers the Apostles, our first bishops, with the authority to forgive or retain sins - and sins THEY do not forgive are NOT FORGIVEN! To expect that sins are forgiven by some other means is to be CONTRARY TO SCRIPTURE. Many non-Catholics will claim that they "go straight to Jesus" to have their sins forgiven, but in doing so they are actually DISOBEYING HIM! He told us who has the authority to forgive sins - so to go elsewhere, even to go directly to Him, is in direct defiance of what He said. Bishops in valid succession to the Apostles retain this authority which was bestowed upon the first bishops. Outside this succession, there can be no forgiveness of sins - by the Word of our Lord Himself.