There is no neutrality between gratitude and ingratitude. Those who are not grateful soon begin to complain of everything. Those who do not love, hate. In the spiritual life there is no such thing as an indifference to love or hate. That is why tepidity (which seems to be indifferent) is so detestable. It is hate disguised as love.
- Thomas Merton
Spiritual infirmities such as tepidity are caused, not only by chills but also by fevers, that is, by excessive zeal.