Long-standing feuds, we've all got (at least) one: the estranged friend, banished family member, the ex-flatmate who you still haven't spoken to since they left the gas on - all are blurred figures in our memory.
Maybe you fell out years ago (so long ago that you've now forgotten the reason for your bust-up) or perhaps the tension is still simmering away.
But whatever the circumstances - and whether you were right or wrong - you should probably extend that olive branch and make up. Or at least try to.
"Holding a grudge or resentment is like drinking poison hoping the other person will die," says David Kessler grief expert, founder of www.grief.com and co-author of You Can Heal Your Heart. "When we stay in conflict with a friend it is our own wellbeing that is disrupted, until we make peace."
Psychologist and HuffPost UK blogger, Dr Raj Persaud says that long-standing feuds can cause a lot of mental strain and, in some cases, rumination - which is a compulsive focus on one's own distress.
"Rumination is not mentally healthy and has been shown by a lot of research to lead to depression," he explains. "Women incidentally appear more prone to rumination than men."
But letting bygones be bygones is easier said than done. It's important to make sure you are fully committed to resolving the issue before you make a move.
On this occasion the devil is not in the detail. A feud will rarely resolve if you remain focussed on who was (or is) right or wrong.
"There needs to be a clear shift in in psychology: from seeking justice to putting the relationship first," says Dr Persaud.
"Sometimes we have to ask ourselves, do we want to be right or happy?" says David.
If you decide that you want to make up, the experts offered the following guidance...
- Reach out: Meet up or call, tell them that regardless of who is right or wrong you miss them. Sending a gift or note may also work
- Rehash the issue: Discuss what caused the break in the relationship, but do so calmly and with an open-mind
- Forgive and forget: Agree to disagree for the sake of the relationship
- Make light of the situation: mock yourself as a way of acknowledging that you have your faults (as they do) and you don't take yourself too seriously
Of course it's not always going to be happy ever after, sometimes the situation will not resolve and you'll have to put the relationship in the past.
This could be down to stubbornness on somebody's part or the reason for arguing could be such an obstacle (for example financial) that it would be a miracle for you to ever make up.
In these cases, HuffPost UK blogger and psychotherapist Bill Cloke thinks we are better off without them.
"The truth is we need to find people in our lives that treat us with respect, kindness, compassion, and empathy. We want to be involved with people who are willing to give something to the relationship and know how to apologise when necessary.
"The rest of them should sod off as it were."