So here a few tips to help you make this happen, remember it is for your child. That makes it worthwhile.
1. Set the Stage: Have an adult conversation about your parenting efforts at a non emotional, relaxed time. Hire a sitter and go to dinner. Examine together what you think you are doing well, and where you might need to tighten up.
2. Agree on the Basics: Find common ground about where you want to set limits for your child and how you will reenforce good behavior, and what you will do when your child's behavior is falling short. The more united you are, the better for your child. Mixed signals from parents are confusing and also grant your child a license to manipulate you, and play you against each other. You need to be in agreement.
3. Look in the Rear View Mirror: Examine the type of parenting you were exposed to as a child, and have a conversation with your spouse or co-parent about how he/she was raised. What did your parents do well, and what were their shortcomings. This exercise can help you both understand why you react the way you do to your own child. Usually we either mimic how we were raised or we swing way to the opposite side of how we were raised, in order to "make up" to our kids for any hurt we felt as a child.
4. Don't Fight In Front Of Your Child: This kind of behavior is damaging to your kid. Promise each other that when you disagree, (which is bound to happen) you will relocate to a different room and hash it out. Remember that you are the adults!
5. Model Respect: Respecting each other is key to having your children respect you in the future. If you call each other names and carry on like preteens, your child will grow up lacking respect for either of you...and that is NOT what you want.
These 5 tips can help your child. So put your ego aside. Stop blaming your spouse or co-parent for all of his/her shortcomings and unite to become better parents. Seek out parenting support if you need it from parenting classes or books or blogs. Working on your parenting skills will bring a closer bond between you and your child, and a brighter future for all of you.