How could it be a health issue?
It may seem less satisfying than holding a grudge and revisiting our moral high ground, but the evidence in favour of forgiveness is clear. It's an investment in our relationships with rewards for both the forgiver and forgiven. Health is just one of the rewards.
Forgiveness makes us resilient because we recover quickly from conflicts. The result: less stress, better mental and physical health - and better relationships. It's an upward spiral. The longest study in the world has established that close relationships are the single most important factor in human thriving.
Doing the honourable thing, especially being forgiving, is a key characteristic of successful intimate relationships. Partners who are close find it easier to forgive, because they choose to.
People who forgive tend to see their partner's bad behaviour in context. They don't judge the whole relationship on the irresponsibility or ill-chosen words that have upset them today. (It doesn't stop them insisting on better behaviour next time.)
The research has focused on marriage partners, but surely doing the honourable thing, seeing the relationship in context and moving on from anger and resentment applies to working relationships too.