Living without grumbling or disputing (Phil 2:14) makes a person "blameless and innocent."
Being blameless is a goal for believers, in general, and a goal, especially, for church leaders (1 Tim 3:2).
Spiritually speaking, this is not a reference to sin or morality, but whether or not a person can be rightfully criticized by other people.
The goal of not grumbling or disputing is not to boast, but rather to live in a way explicitly different from the depraved world we find ourselves in. All true believers are children of God (Jn 1:12–14).
However, to live without blemish as God's children requires diligent effort. Part of the reason this is difficult is because of the sin inherent to the world around us.
Believers are to be in the world, not of it. Being of the world, leads them in to difficult situations, and temptation. Yet believers are called to stand out as unique and powerful examples: as "lights in the world."
Paul's words closely resemble Jesus, who taught, "Let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven" (Matt 5:16).
Phil 2:12–18 explains how Christians ought to live, considering all that Christ was willing to do for them. The command to ''work out'' salvation is a directive to let the new birth in Christ translate into actions.
As a part of this, believers should serve God without griping or complaining. Paul knows that his service to God has been hard, but this is simply another form of offering. All Christians are invited to serve in the same selfless way.
Trust God’s Word, no matter what.
Keep your eyes on the horizon.