Until a man’s earthly life finishes its course, up to the very departure of the soul from the body, the struggle between sin and righteousness continues within him. However, high a spiritual and moral state one might achieve, a gradual or even headlong and deep fall into the abyss of sin is always possible. Therefore, communion of the holy Body and Blood of Christ, which strengthens our contact with Him and refreshes us with the living streams of the grace of the Holy Spirit flowing through the Body of the Church, is necessary for everyone.

St. John of Shanghai and San Francisco

Every Christian should find for himself the imperative and incentive to become holy. If you live without struggle and without hope of becoming holy, then you are Christians only in name and not in essence. But without holiness, no one shall see the Lord, that is to say they will not attain eternal blessedness. It is a trustworthy saying that Jesus Christ came into the world to save sinners (1 Tim. 1:15). But we deceive ourselves if we think that we are saved while remaining sinners. Christ saves those sinners by giving them the means to become saints.

St. Philaret of Moscow

If you would be victorious, taste the suffering of Christ in your person, that you may be chosen to taste His glory. For if we suffer with Him, we shall also be glorified with Him. Blessed are you if you suffer for righteousness' sake. Behold, for years and generations the way of God has been made smooth by the Cross and by death. The way of God is a daily Cross. 

St Isaac of Syria