Courage is a virtue, indeed - as CS Lewis said - it is "the form of every virtue at the testing point". In other words, unless the other virtues are sustained by courage, they will be discarded whenever inexpedient.
The evil-twin vice mimicking courage is recklessness; which is act inexpediently because you don't understand that it is inexpedient.
A reckless person might therefore endanger himself be falsely believes himself invulnerable ("it's not really dangerous", "it couldn't happen to me!") or because he wrongly regards the adverse outcome as trivial ("getting shot isn't that bad.").
Courage, on the other hand, is when the inexpedient is done despite the understanding that it is inexpedient - but done anyway for reasons that go above or beyond expediency.
This is why there is so little courage nowadays - simply because very few people are strongly motivated by reasons 'above and beyond'.
For Christians, who do have reasons above and beyond; the source of courage is easy to state, but harder to do: It is simply to live by Faith and in Hope.
Faith is that God - who is the creator and sustainer of this world, and our loving Father - will always be-arranging-things for our ultimate spiritual benefit.
No matter what evils are practiced by Men or demons; God will turn that real evil to the possibility of ultimate and eventual Good.
And for each of us, as specific individuals.
Hope is based-on knowledge that beyond this finite mortal life, there is the possibility of eternal resurrected life in Heaven; and that is available to any and all who choose to follow Jesus Christ.
Therefore, for a follower of Christ, the worst that can happen in this mortal life will pass and be succeeded by something far better and forever.
Thus Faith and Hope underpin courage, and are the antidote to fear.
(And also the antidote to that lethal sin: despair.)
Furthermore; Faith and Hope themselves feed-into the affairs of this mortal life via the courage they sustain, and the virtues they enable. Precisely because rooted in the next world; Faith and Hope will materially benefit life in this world, and give the best chance of good outcomes - no matter how bad things may get.