If someone has done or said something grudgeworthy, but it's the only grudgeworthy thing they've ever done, should we always let them off and treat is as a mere blip? Is it possible to sustain long friendships and relationships in which no grudgeworthy behaviour occurs? Should everyone get at least one 'get out of grudge free' card? And how relevant are patterns of behaviour and track record when assessing the grudgeworthiness or otherwise of a particular action? Sophie talks to psychotherapist Helen Acton about a recent 'blipping' involving an otherwise lovely close friend — should she hold a grudge or not?