You only have to forgive once. To resent, you have to do it all day, every day. You have to keep remembering all the bad things.

So says M.L. Stedman in her 2012 novel The Light Between Oceans, released last year as a motion picture starring Michael Fassbender, Alicia Vikander and Rachel Weisz. (Disclaimer: I have neither read the novel nor seen the film. This is me writing with my deacon / Catholic blogger hat, not my film-critic hat.)

In the novel, the speaker goes on to say, “I would have to make a list, a very, very long list and make sure I hated the people on it the right amount. That I did a very proper job of hating too.” In the film, this line appears to be abbreviated to “It’s too much work.”

Well. All this is a very pretty idea, but it’s, um, the opposite of right.

The reality is that resentment for a past wrong is a temptation that may recur over and over no matter how often one has chosen to forgive. As C.S. Lewis puts it in Letters to Malcolm: Chiefly on Prayer:

To forgive for the moment is not difficult. But to go on forgiving, to forgive the same offence again each time it recurs to the memory — that’s the real tussle.

Not necessarily, certainly, and not always. Sometimes forgiveness is effortless. Other times it’s an ongoing battle. Forgiveness may come more easily to some than others — and on behalf of some than others — and in connection with some offenses than others.

The bottom line, though, is this: Jesus tells us to forgive 70 times 7. That could involve 70 times 7 offenses — or just one.

The idea that holding a grudge is “too much work” is a strange half-truth. It is true that forgiveness is liberating and resentment is soul-crushing. As Martin Luther King Jr. said, more broadly, “I have decided to stick with love. Hate is too great a burden to bear.”

But there’s a paradox here. Hatred and resentment are soul-crushing in their effects, but they’re not hard to do — and, once you start, by a kind of spiritual inertia or momentum, it gets easier and easier.

Conversely, love and forgiveness are liberating in their effects, but they can be very hard to do, and keep on doing. Sometimes this too gets easier with time, but the temptation to fall back into hatred and resentment may crop up at any time, and must be fought off each time.

Resentment is deadly. Whoever said “Holding a grudge is like drinking poison and expecting the other person to die” was onto something. But forgiveness can be a bitter drink — far bitterer than the intoxicating draught of resentment. And you may find there’s always a bit more to swallow than you thought, even if it does get easier and even sweeter later on.

Note, by the way, that “intoxicating” can mean both a) exciting or stimulating and also b) debilitating (i.e., adversely affected by toxins); it also connotes addictiveness. Resentment is potentially all of these.

It’s good to emphasize the wholesomeness and liberation that comes with love and forgiveness, and the burden that comes with hatred and resentment. But let’s not forget there’s a reason the road to destruction is broad and well-traveled, while the way to life is narrow and less frequented.