Do not forget that assurance is a thing that may be lost. Oh! it is a most delicate plant. It needs daily, hourly watching, watering, tending, cherishing. So take care. David lost it. Peter lost it. Each found it again—but not until after bitter tears. Quench not the Spirit; grieve Him not; vex Him not. Drive Him not to a distance by tampering with small bad habits and little sins. Little jarrings make unhappy homes, and petty inconsistencies will bring in a distance between you and the Spirit. The nearest walker with God will generally be kept in the greatest peace. The believer who follows the Lord most fully will ordinarily enjoy the most assured hope.
– J. C. Ryle