That every one is tempted so much as he is able to bear
In the first Epistle of Paul to the Corinthians: No temptation shall take you, except such is human. But God is faithful, who will not suffer you to be tempted above that you are able; but will with the temptation also make a way to escape, that you may be able to bear it.
Source: The Treatises of Cyprian (New Advent)