They are aware of, own, and are able to articulate their thoughts, feelings, and beliefs. They honor their differences and appreciate their partner for the unique perceptions, experiences, and preferences that make that person who they are.
They decide together how to be a couple. They agree on some basic terms for how they will handle issues such as relationship boundaries, finances, chores, and parenting. In an adult to adult relationship, spouses are sensitive to each other's feelings and opinions and keep the other person and the relationship in mind when making personal choices. They take each other's feelings and concerns into consideration, but don't feel forced to do or not do things because of "shoulds" or "should nots" set out by their partner. . Decisions are made colaboratively in a climate of mutual respect and caring.
In adult to adult relationships, partners don't try and change each other through manipulation, bullying, threats, guilt trips, or emotional blackmail. They don't demand that their spouse or date conform to their expectations or wishes. They don't pressure or badger the other person to "give in" when they're not getting their way. They don't throw tantrums, pout, turn on the waterworks, or resort to verbal "low blows." They don't insist on always getting what they want or on always being right. Relationships that operate this way are adult/child relationships, even if both partners are adults in actual age. We all know forty year olds who can act like four year olds.
If you are confused about how healthy your relationship is, it may help to talk with a third party you feel comfortable with. This could be your personal physician, a pastor or other religious leader, a family member or friend who seems to be in a solid relationship, or a qualified counselor or relationship coach. Everyone deserves to be treated with kindness and respect in their close relationships. No one's marriage or romance is perfect or happy all the time, but its important to feel valued and as though you are seen as an adult.