That is morality, principles and values to guide our behavior through life. It's an incomplete morality, but not different from morality.
Without something else, you're right, it's unstable and degenerates. I think Christianity's probably the most proven solution, but not necessarily the best for everyone today nor the best that will ever exist. After all, it's not without examples where it has degenerated as well.
Objectivists would say that an understanding of a single non-subjective reality with predictable consequences of bad behavior, "that which doesn't promote life", that guides our principles replaces the role of God for them as a foundation for morality. Personally, I think they have great potential, but aren't nearly as far along as most think they are to developing a stable, complete and self-sustaining moral system similar to that of Christian communities.
Provide one example where a man remaining in fellowship with God, through Christ, indwelt and filled with the Holy Ghost has degenerated without the man first drifting away from God via Christ and denying the Holy Ghost, by acting or even thinking first independently of God's will.