"Question: How shall we know that God has a purpose to save us?
Answer: By being effectually called. "Give dilligence to make your calling and election sure" (2 Peter 1:10). We make our election sure, by making our calling sure. "God hath chosen you to salvation through sanctification" (2 Thess. 2:13). By the stream, we come at last to the fountain. If we find the stream of sanctification running in our souls, we may by this come to the spring-head of election. When a man cannot look up to the firmament, yet he may know the moon is there by seeing it shine upon the water: so, though I cannot look up into the secret of God's purpose, yet I may know I am elected by the shining of sanctifying grace in my soul. Whosoever finds the Word of God transcribed and copied out into his heart, may undeniably conclude his election."
-Thomas Watson "All Things for Good"