Are all true believers at all times assured of their present being in the estate of grace, and that they shall be saved?

Assurance of grace and salvation not being of the essence of faith, true believers may wait long before they obtain it; and, after the enjoyment thereof, may have it weakened and intermitted, through manifold distempers, sins, temptations, and desertions; yet are they never left without such a presence and support of the Spirit of God, as keeps them from sinking into utter despair.