SELF-DISCIPLINE IS NORMALLY A GOOD THING.
Indeed, Christians believe that God has given them "a spirit of power, of love and of self-discipline" (2 Tim. 1:7). But certain forms of self-discipline are ignoble, even dangerous.
For example, the Stoics in the days of the apostle Paul thought that it was the part of wisdom to live in harmony with the way things are in the world, and that this entailed living apart from the "passions," in perfect accord with reason. Motivated by high moral principles, they prided themselves in living above the emotions, above deep personal commitments that could bring suffering. At one level, such "stoicism" is admirable. But it is a long way from the personal commitments that the Gospel mandates, complete with the vulnerability and suffering that are a part of this fallen order. In fact, that is the problem with the Stoic worldview: its view of the world and what is wrong with it is so far removed from what the Bible says that it defines what is good in ways that owe more to a certain kind of pantheism than to anything else. So from a Christian perspective, even if there is something admirable to Stoic self-discipline, it can never be judged genuinely good. Some self-discipline merely puffs people up with the pride of resolution.
Another kind of questionable self-discipline occurs in the opening verses of Psalm 39. David has resolved not to speak. It is not entirely clear whether his self-disciplined resolution not to say anything, especially in the presence of the wicked (39:1), is motivated by fear that otherwise he is in danger of joining them, or more likely out of fear that if he speaks he will let slip something that might be dangerous in this company, or simply out of some misplaced conviction that it is enough to keep silent and not lend them support. Clearly, however, it was a moral resolve, in some ways commendable — and wholly inadequate. For as he kept silent, he did not even say anything good (39:2).
One way or another he was trying to beat sin by disciplined silence.
David learned a better way. He speaks — but in his speech he addresses God (29:4ff.). He is aware of life's fleeting passage, and concludes that, in the end, we have nothing to look for except to put our hope in the Lord (39:7). God alone can save us from our transgressions and enable us to escape the snares of opponents (39:8). Resolute silence in the face of the mystery of providence is no way forward (39:9); it is a false self-discipline, an ugly defiance rather than a cheerful submission to God's "discipline" (39:11).
Numbers 5; Psalm 39; Song of Songs 3; Hebrews 3