Eye opening! Timshel = thou mayest. Thou mayest what? Thou mayest triumph over sin. Of course, as Christians, we know the only way to triumph over sin and its effects is through Jesus Christ. Through dying daily to that sin. In realizing that Christ has taken that sin upon himself.
I also think, though, that as Christians, we have been given the ability to not sin. To not give in to its grip on us. To not give in to our desire to rule over ourselves. When we give into that desire and let sin get a grip on us, death ensues. Death is always the result of self-rule.
Self-rule will lead us down many paths that we never could have even imagined. Lying, stealing, adultery, greed, dishonoring your family, cursing God's rule and turning your back on the image he made you in and the vocation he has called you to. Eventually, as the Bible shows us many many times, self-rule leads to murder, suicide, death.
How is this self-rule overcome? By taking God at his word. He told Adam and Eve what would happen when/if they decided on self-rule. He told Cain what would happen if he didn't take a hold of his sinful desires. He told Israel (the nation) exactly what would happen when they decided on self-rule. We could go on. The way out of self-rule is to listen to God, to take his word as truth, to know that he will follow through on his promises - be they good or bad.
What about those who claim to take God and his word seriously and yet choose self-rule? Are these two compatible? Can those who chose self-rule, which eventually leads to death, enjoy communion with God, whether on this side of life or the other? If self-rule ends in death, will life everlasting await the one who lives by it?