A secure faith

As we've been reading the book of Job together in our SPA groups, the issue of God's sovereignty is brought into sharp focus against the backdrop of suffering.
In my quiet times, I've been reading 2 Corinthians. At first glance, it appears as though Paul is holding divine sovereignty and human responsibility in tension: so, in 1:21 he says, 'Now it is God who makes both us and you stand firm in Christ. He anointed us, set his seal of ownership on us, and put his Spirit in our hearts guaranteeing what is to come.' But then in v24 he says, 'we work with you for your joy, because it is by faith you stand firm.'
So can we say both that God makes us stand firm and that we make ourselves stand firm by having faith?
Perhaps not. Paul is clear in Ephesians 2 that even our faith is a gift from God (v 8).
And yet, when the man comes to Jesus in John 6:28 and asks, 'What must I do to do the works God requires?' Jesus replies, 'The work of God is this: to believe in the one he has sent'. Here, 'the work of God' isn't the work God does, it's the work God requires of us, and that work is, 'to believe in the one he has sent' (i.e. Jesus).
So our faith is required of us and is the gift of God. This is hard for us to understand - how can something be required of us and God's gift to us? But the Bible constantly teaches that God is absolutely sovereign and that we are responsible for our actions. The classic summary is Genesis 50:20,

'As for you, you meant evil against me, but God meant it for good, to bring it about that many people should be kept alive, as they are today.'

And this comes to a climax at the cross:

'This man [Jesus] was handed over to you by God's set purpose and foreknowledge, and you, with the help of wicked men, put him to death by nailing him to the cross.' Acts 2:23 

So God uses our actions to achieve his purposes. Some people kick against this, thinking that they have absolute freedom. But one of the purposes of God's long speech to Job in chapters 38 & 39, with its relentless questions raining down on Job,  is to force him to acknowledge that he has no power to control anything in all creation and that God is in control of everything. It's only when Job is able to acknowledge this in silence (40:4f) that he's able to make progress in understanding God.

Back, then, to the issue of 'standing firm in Christ'. Is it us or God who makes us stand firm? Well, we are commanded to stand firm, but behind our resolve stands God's grace and mercy which enables us to obey the command.