How can I have faith in times of crisis?
You must cultivate and preserve a confidence in God when you are not in a crisis. If we wait until a crisis comes then we won't have the resources or the depth necessary to maintain our faith well.
Cultivate a deep confidence in the love and power of God day by day. Develop daily disciplines of communion with Christ so that you grow steadily. Grow so that when crisis comes your roots will be sunk deep in grace and the fiber in your tree will be solid. Then you won't be as fragile as so many Christians seem to be when crisis comes.
Good times tend to lull us into sleep and spiritual indifference as though our faith will just take care of itself when the crisis comes, which simply isn't the case. But that is why so many Christians, instead of casting themselves on the Lord with a deep and quiet confidence in the midst of crisis, shake their fists in God's face and say "Where are you?" They haven't come to know that God is sovereign, loving, and caring in the hard times as well as the good.
We must nurture our faith with the full biblical portrait of a God who is sovereign over both evil and good, so that when either one comes our confidence in him will not be shaken.