One of the greatest truths I have learned from Piper is that saving faith is one that looks to and rest on God’s promises in Christ for salvation, both in the past, present and future.
“A second assumption is that justifying faith is not only a trusting in the past grace of God, but also a trusting in the future grace of God, secured by the past grace of Christ’s death and resurrection. Justifying faith embraces the finished work of Christ’s atonement, in sense that it rests in all that this atonement means for our past, present and future.” 
Also to my amazement, Wright articulates something similar to Piper:
“The doctrine of justification by faith is that all this is even now certain for those who believe in the Gospel; the experience of justification by faith is the steadfast looking away from oneself at the objective facts of incarnation and atonement, revealing as they do the unchanging and unshakeable love of God for his people. This is justification: because of the work of the Son and the Spirit, God pronounces in the present the future verdict of 'righteous' over all who believe. Irrespective of moral or racial background, believers are declared to belong for all eternity to the true people of Abraham, the family of the renewed covenant, the people whose sins are forgiven.” 
“The 'faith' in question is faith in 'the God who raised Jesus from the dead'. It comes about through the announcement of God's word, the gospel, which works powerfully in the hearts of hearers, 'calling' them to believe, or indeed (as Paul often puts it) to 'obey' the gospel (
 John Piper, “Future Grace”, pg. 27
 N.T. Wright, “Justification: The Biblical Basis and its Relevance for Contemporary Evangelicalism”