While my salvation may not be threatened by the sin in my life, neither may I become complacent about it. If I continually and unrepentantly defy God in some area, the sincerity of my commitment can be called into question. While one could not conclude that my faith is non-existent, it may be abundantly clear that it is small and relatively unimportant to me. And so, I strive to avoid sin. I study God's Word to so fill my mind with His thoughts as to push out the influences of a world that is indifferent or antagonistic to Him. When I fail, I ask forgiveness and rely on the salvation I have already received.
Please read that last sentence again. I do not ask forgiveness to achieve a new salvation, or a new level of salvation, or just enough salvation to cover whatever wrongs I've done since the last time I asked. As soon as I committed my life to Christ, I was saved, I am saved, and will continue to be saved forever. I was/am/will be justified before God, once and for all. It is a simple truth, though often overlooked, that justification and forgiveness are two different things. They reflect two different aspects of our relationship with God. In fact, they may be thought of as two separate relationships, one judicial, one personal.
I've been married since 1983. I love my wife, and try to do my best by her. I sometimes fail. I get grumpy or selfish or over-sensitive or all three at once and I sin against her. Does this automatically make us unmarried? Have I, in my thoughtlessness, dissolved all legal ties with her? Do we need to find a preacher and have another wedding? Of course not. I have, however, damaged the personal relationship. My wife is hurt, possibly angry. The intimacy of our marriage is broken until such time as I am forgiven by her. That usually doesn't happen until I demonstrate that I truly am sorry for what I've done and want her forgiveness. In our flawed world, continually breaking the personal relationship can lead to the couple taking the legal step of separation and divorce. But, no one becomes unmarried accidentally. As it required a specific act of will and law to construct a marriage, so it requires a specific act of will and law to dissolve a marriage.
And so it is with my "marriage" to God. He is my judge, but that judgement has already been decided and carried out. I cannot simply fall out of grace. God's enemies may push, prod, and provoke, but they cannot break the legal ties that bind. The relationship cannot be changed by anything less than the same specific act of will on my part which helped bring the relationship about. Many maintain that even that can't do it. Still, I can hurt Him. My sin offends and angers Him. Our personal relationship suffers until I acknowledge and repent of that sin. For His part, God is eager to forgive and restore that intimacy.