"But I pray to you, O Lord, in the time of your favor, in your great love, O God, answer me with your sure salvation." Ps.69:13
Your salvation is SURE - there is no guesswork. Once you have stepped into a relationship with God through Jesus Christ "It is finished."
We don't step outside our door each morning wondering if gravity will be in effect - it's a given - an absolute.
Salvation is more sure than gravity. Salvation is a product of who God is - gravity is only one of His creations.
Praise be to God whose love is great.