WE HAVE all sat with someone who cannot let go of a grievance. We might even have suggested that they begin to let go of it - but why should they, especially when justice is on their side?

As a recent TV episode of Crimewatch reminded us, three-year-old Madeleine McCann disappeared from her family's holiday apartment in Praia da Luz in May 2007. In child abductions, the first six hours is regarded as crucial for successful recovery; it is now more than six years, but her parents remain determinedly active in pursuit of their daughter. She leaves a hole that cannot be filled in their family.

Brian Hambleton is also a man pursuing justice. In November 1974, his 18-year-old sister, Maxine, was killed in the Birmingham pub bombings, in which 21 people were murdered by the IRA. After the release of six falsely convicted men, the real perpetrators remain free, which Mr Hambleton cannot accept.

He recently picketed a peace rally that Gerry Adams attended. "You've got Gerry Adams inside spouting about peace and reconciliation," Mr Hambleton said. "He needs to address his past before he can go forward. You can't have peace and justice without the truth. Why isn't he forthcoming with the names of the perpetrators who killed my sister and all the other victims on the mainland?"

Patrick Hill, one of the Birmingham Six, said last year that they had learned the names of the real bombers, and claimed that it was common knowledge among the upper echelons of the IRA and British government. So why should Mr Hambleton give up?

Sometimes, we baptise our fixations by calling them "the pursuit of justice". We lock on to a person or an outcome with a sense of grievance. It is a negative relationship that we justify in a hundred different ways, but it can render us ill.

Our lives become defined by a complaint we cannot put down. It is one thing if it is a work grievance - a sense of injustice when passed over for promotion. But what if it is abduction or murder; and what if it is family? Do the principles change?

Our response to loss is a personal affair, with no template for the experience. Loss does not always become grievance; sometimes we will simply pass from loss to sadness to acceptance, although with loss, nothing is simple. And if there is grievance, this, too, may pass in time, unable to linger amid the good in our lives. We let go.

Sometimes, however, the gnawing feeling remains, an ache that will not leave, and we become defined by its force, demanding "justice" to ease our pain. It seems weak to let go, a betrayal even. Yet fixation eats at the soul, and the boundary between fixation and justice is not well-marked. We proceed with discernment.

Angela Tilby is away.