Salvation is only possible as a result of Christ's work. However, this work is not over! Christ continues to work within each and every one of us through His Abiding Presence in transforming us. But we can reject His graces. So, yes, we have some part to play in salvation, but it is a more passive role as we don't earn anything, we are merely giving back the gifts of love that God has enabled us to do.
Regards
Hebrews 1:3
Who being the brightness of his glory, and the express image of his person,
and upholding all things by the word of his power,
when he had by himself purged our sins, [no co redeemer needed.]
sat down on the right hand of the Majesty on high.....
Hebrews 10:12
But this man,
after he had offered one sacrifice for sins for ever,
sat down on the right hand of God;
13 From henceforth expecting till his enemies be made his footstool.
14 For by one offering he hath perfected for ever them that are sanctified.
The work is over.