Luke 2:29 (NIV)
This verse should help clarify that Simeon believed that he had one foot in the grave. It clearly reveals a man who believed in a Sovereign God; not Sovereign like the Queen of England (who sits on a throne a long ways away from Canada and who has nothing to do with the personal lives of her "subjects"), but a God who is personally and intimately involved in the lives of each of His subjects.
This God instructs us to call Him, Father, and He, Himself, not another, decides when to "dismiss" us. An older friend of mine, while talking with me about the death of a Christian brother, remarked, "God let him out of class early." That is "dismissal"; being released from the school of life on this broken earth. Who decides when you or I will be "dismissed"? The Sovereign Lord does!
This children of older people struggle to answer the question of their parents as they ask, "Why am I still here?" Simeon knew that he was alive so that God's personal promise through His Spirit to Simeon, could be fulfilled. To be "dismissed in peace" is to be blessed. There will be grieving, for there is separation from loved ones, but to die in peace with God should be on ever human's bucket list!
It is worth noting that Simeon's peace came after and through seeing the Messiah who is Jesus of Nazareth. I think of Stephen crying out: "I see heaven open and the Son of Man standing at the right hand of God" (Acts 7:56). Oh to see Him. To gaze upon His beauty. To see Him in His holiness! Simeon was dismissed in peace. Stephen was dismissed in peace. May each of us leave this world in peace; the peace that passes understanding. The peace that comes to us from God through His Son, the Lord Jesus Christ.