Relationship friction, duty and responsibility, power struggles, ego-related conflict

A character looking after their household and children while an overcommitted or ungrateful spouse pursues their career goals 
Being expected to work long hours without extra pay or recognition
The character supporting an unappreciative, selfish, or manipulative friend through difficult times and them not returning the favor
The character constantly sharing their possessions—a car, internet bandwidth, clothing, etc.—with an entitled friend or roommate
A parent financially supporting an adult child who, in turn, expects them to do so
The character taking on the lion's share of work (at school, on the job, when volunteering or child-rearing, etc.) while their peers do little or nothing
The character always being asked to do favors or take on unpleasant jobs
Not ever being acknowledged for the way the character contributes (to a business, marriage, friendship, as a caregiver to an elderly parent, etc.)

Missing time with family and friends due to extended work hours
Having to miss an anticipated event to help with someone else's "emergency"
The character becoming so dissatisfied at work that they quit or decide to look for another job
Having houseguests who overstay their welcome, hindering the character's personal life
Having to make personal sacrifices because they're giving their money to others
Giving up things the character wants—turning a craft room back into a bedroom, missing out on social activities, etc.—to meet the needs or desires of others
Work quality being affected because of exhaustion or distraction
Domestic disputes arising from an imbalance of responsibilities
The character being inconvenienced in their own home (because a house guest is messy or ignores established quiet times)
Awkwardness arising when the character sets boundaries with others
The character losing interest in things they used to enjoy
The character gravitating toward relationships with people who don't take them for granted but are bad for them in other ways (having an affair, getting involved with an abuser, etc.)