When I'm teaching my Creative Writing MA students, I like to remind them that most people think of themselves as the hero of their life story. We invent narratives for ourselves to help explain our lives, we turn our lives into story - hence, life story. But if we're the hero of that narrative, doesn't that mean we also have an antagonist, an arch enemy, a foe to fight?
[Excuse me while I continue driving this train of thought along...] Now, I doubt most people have a single nemesis that last their whole lives from childhood, through school into jobs and careers, before a final confrontation that leads to the death of either [or both] individual. That epic struggle would be a bit over the top, unless you've a very fraught family life.
More likely there's a series of people with whom you come into conflict at different points in your life. The person at pre-school who got the attention, the affection or the toys you wanted. The person at school who bullied you or did better at subjects you loved or got the position in the sports team you craved. The person at work who got your promotion, and so on.
I guess in real life these people aren't your arch enemy, they're your competition. But in life stories they become more mythic - the mother who belittled you, the bully who humiliated you, the jerk at work who got their comeuppance. It's what we do, we create stories to make sense of our lives. But there's another side to that coin you might not have considered.
While you're casting other people in your life as villains of a situation, somebody else could be casting you as their arch enemy. If you excelled in a class, other students may have envied, even hated you. If you got a promotion, others may have felt embittered that they missed out. If you have children, those who don't may wish they had your family situation.
Not sure where I'm going with this, but there's at least two sides to every story. Thinking about all those points of view may be time consuming, but it could lead to a deeper understanding of all the players, their motivations. That should lead to better stories. How you apply that understanding in real life is another matter. Onwards!