There are two different definitions of "commitment". One definition is being sent to an institution. The other deals with making and keeping pledges or promises to another person.
Some couples have troubles with commitment because they confuse the two definitions. They are afraid that commitment in a relationship means getting into an institution with too much structure, control and barriers to their freedom to be themselves.
They are wrong. A commitment is a freeing and growing experience. When two people make a commitment to each other to grow, learn about life and love together, they are creating a positive place to be. A commitment is an act of trust, both of yourself and of your partner.
Some couples choose to commit themselves to each other for life, through a marriage ceremony, either religious or civil. Some couples haven't reached that stage of formal public commitment decision. They may not know if or when they will reach it.If a relationship is to have a chance, people must make their own commitments between themselves about their goals and expectations, as individuals, and as partners or lovers.
Commitment to a relationship is "a pledge to bring all of oneself and all of one's truth into a mutually defined and sexually monogamous experience with another person."
Commitment requires you to explore, develop and nurture a co-created boundary around a relationship. You have to work together at it. You each need personal autonomy within that relationship, but you also need to recognize, honor and respect those agreed-upon and shared boundaries as well.
Boundaries aren't static. They may need to change over time. This requires both of you to acknowledge and continually review what you expect of each other as the relationship grows. For example a woman who initially wanted and agreed to be a stay-at-home mom, may a few years later, find that her needs have changed. That means revisiting the earlier agreed-upon commitment.
You can't demand boundaries in advance, or impose them on your partner, since you don't have the right to be charge of the other person. You have to negotiate them. People who try to impose on their partner tend to have short-lived relationships. People want to be loved and cared for, not controlled or ordered.
Besides agreeing to work on issues that you are important to both of you, it is important to recognize your differences, and make a commitment to respect these differences.
You are both human. It is possible one or both of you may step outside those boundaries of what is seen as acceptable at some time. This doesn't mean the relationship is automatically over, unless one of you makes that decision on your own.
You need to learn about and practice forgiveness, when your partner makes mistakes, is unfair or even hurtful. We all make mistakes. If we expect our partner to tolerate and accept our mistakes, we must also forgive our partner's mistakes.
This means both of you have to work actively at forgiving the behavior of the other, and forgiving yourself as well, for your own mistakes. That is a tough part of a commitment, for when you feel hurt, it is not that easy to forgive. But  you can succeed.