How long would you hold a grudge for? How long could you hold a grudge for?
There is no definite answer of course , nor is there a right or wrong answer… It merely depends on what type of person you are.
Perhaps holding a grudge should be needed if someone holds a grudge against you. But saying that, wouldn’t that eventually make you paranoid? The constant feeling that you have to watch over your shoulder because you know someone has something against you… Surely that can’t be good for you.