Conflict at a personal level is essential in any story and comes in various degrees and flavors. It can be anything from good-natured bickering to abusive and anywhere in-between. It’s another way to add depth to your characters and their relationships. Few can say, at least honestly, that they get along with everyone. There’s bound to be someone, or some type of someone, that drives you crazy.
If everyone is fighting all the time, then that can get grating, too. Like so many other things, balance is required. However, if everyone always gets along and is happy continually, that’s going to get pretty boring, mostly because it’s not a representation of life. Even fairytales have conflict, often brutal and lots of it. How many of those stories should be investigated by Children’s Protective Services? But how much of a story would it be without that element?
Conflict between characters makes a story come alive. It doesn’t necessarily have to be your main characters. Secondary characters are fertile ground for introducing personality conflicts.