I believe we are punished by our sins, not because of them. That is, we reap the consequences of what we sow, in this life or the next. The greatest pain is when we stand before God and realize the horrors of what has happened because of our sins, the pain we have caused to others and to God, who is in all things and feels that pain as well. If we are followers of the Christ, the Light of God dwells in us, and we are saved through God's grace. The reason for this is not simple belief, but rather real inward change, the result of which we repent for our sins now and are spared from experiencing the pain we have caused after our death when the truth is laid bare to all. In essence, we feel the pain our sins cause as we go through life and are able to be buffered from their full force, because we have chosen to tackle them now and cut them out as much as possible.
If we handle our sins during our lifetime, and are truly saved (that is, living as followers of the Christ), then we naturally increasingly desire to do good for others rather than to cause pain, we see our errors more consistently, and we strive to repent. It is not our works that save us, but our works are a natural consequence of our inner focus. You know... where your heart lies, there is your treasure also.
To me, there is no forfeiting salvation, but true salvation comes with inward change, a choice to kindle the flame of the Spirit that is in all people into a roaring fire, refining both our focus and our actions. Without this inward change, salvation and belief are merely empty words. With this inward change, our entire self and reality is altered, and we are never the same. We may stumble, but the constant thirst to be at one with God keeps us striving to become more Christ-like.
I should note that I am not a conservative Christian, so my concept of following Christ is quite different than some might interpret. I am not referring to beliefs or going to church and so forth. I am referring to the spirit of Christ's message and life; the deep meaning behind the gospels. People can come to follow the living Christ through the Bible and Christianity, or inadvertently come to this path through other means (religions, philosophies, simple love for humanity and the earth). It is unconventional, but I really believe that salvation is found in embracing Christ's path, the heart of the Message, not just in joining a certain religious group or praying a prayer. It is a turning toward God's grace, which can appear in any number of forms. But I would put forth that meeting someone who is truly following Christ is distinctive and remarkable, no matter what their outward religious affiliation. You can see God's work in and through them in the fruits of the Spirit, and this is evidence of their inward change.