Everyone who has ever gotten on a plane knows about the emergency procedures in case of rapid loss of altitude. Between a mother and a child, who gets the oxygen mask first? It is more important for the mother to be able to breathe than it is for the child. Why? After the mother can breathe, she can think about and do what is necessary to save the child. However, if the child is saved first, s/he doesn't have the necessary skills to think about and do what is necessary to save the parent. If the parent is saved, they both are. If the child is saved, the parent is lost.
This scenario equally applies to parenting in general. Yes, our child is very important. To many of us, s/he is the most important thing we will ever have an effect on. Nevertheless, if you lose yourself in the parenting process, you will run out of air and suffocate. We are allowed to make time for ourselves, to recharge and recuperate. Single parent homes are the most obviously at risk for failing to allow the parent to breathe, but two parent homes are not immune. It is foolish and dangerous, not praiseworthy and self-sacrificing, to ignore your needs to socialize with friends & family so your child doesn't miss a single bedtime story time.
Now, on the other extreme, it's unhealthy in a different direction to ignore your child and his/her right to live and enjoy life. The best approach is to find a middle path, a balance of selfish time and selfless time. Look into yourself, identify a hobby or activity that you enjoy, which requires minimal external support, and set a time, for one or two hours each week to do this activity. For example, I enjoy hiking, so I built for myself a list of all trails within a 100 mile radius of where I live. Every Sunday, I get up before my family, drive out to a trail I haven't visited in a few weeks, and spend one-hour hiking. There's a playlist of podcasts I listen to while hiking, learning about and listening to information I care about. After an hour, I turn around and spend an hour hiking back to my car, whereby I drive home and start my day with the family. This is my time to recharge my mind and body, setting the tone for the rest of my week. For the rest of the week, I'm free to devote my time to my work and my family, knowing that I've first taken care of me. Right now, make an appointment with yourself, write it down in your calendar. Use that time to pick something you enjoy, be completely selfish, make a weekly schedule to allow yourself to indulge in this one activity.
For an additional boost to your self-care, reach out to one very close friend, and agree to meet once per month. It doesn't matter if your monthly social time is fifteen minutes over coffee or a two and a half hour movie at the local cineplex, or if it's coffee one month and a movie the next month. The goal is to be consistent in making and keeping time for the relationships in your life that matter to you.