He grew downward in humiliation before God, and he grew upward in his adoration of Christ.
Handley Moule captures the essence of Simeon’s secret of longevity in this sentence: “‘Before honor is humility,’ and he had been ‘growing downwards’ year by year under the stern discipline of difficulty met in the right way, the way of close and adoring communion with God” (Moule, 64). Those two things were the heartbeat of Simeon’s inner life: growing downward in humility and growing upward in adoring communion with God.
But the remarkable thing about humiliation and adoration in the heart of Charles Simeon is that they were inseparable. Simeon was utterly unlike most of us today who think that we should get rid once and for all of feelings of vileness and unworthiness as soon as we can. For him, adoration only grew in the freshly plowed soil of humiliation for sin. So he actually labored to know his true sinfulness and his remaining corruption as a Christian.
I have continually had such a sense of my sinfulness as would sink me into utter despair, if I had not an assured view of the sufficiency and willingness of Christ to save me to the uttermost. And at the same time I had such a sense of my acceptance through Christ as would overset my little bark, if I had not ballast at the bottom sufficient to sink a vessel of no ordinary size. (Moule 134f.)
He never lost sight of the need for the heavy ballast of his own humiliation. After he had been a Christian forty years he wrote,
With this sweet hope of ultimate acceptance with God, I have always enjoyed much cheerfulness before men; but I have at the same time laboured incessantly to cultivate the deepest humiliation before God. I have never thought that the circumstance of God’s having forgiven me was any reason why I should forgive myself; on the contrary, I have always judged it better to loathe myself the more, in proportion as I was assured that God was pacified towards me (Ezekiel 16:63). . . . There are but two objects that I have ever desired for these forty years to behold; the one is my own vileness; and the other is, the glory of God in the face of Jesus Christ: and I have always thought that they should be viewed together; just as Aaron confessed all the sins of all Israel whilst he put them on the head of the scapegoat. The disease did not keep him from applying to the remedy, nor did the remedy keep him from feeling the disease. By this I seek to be, not only humbled and thankful, but humbled in thankfulness, before my God and Saviour continually. (Carus, 518f.)
Please do read it all.