"Love is what is left in a relationship after all the selfishness is taken out" Cullen Hightower
What seems to get muffled is 'parenting and selfishness' and mostly that occurs because of the family dynamic you find yourself in.
I'd hope you would never throw away your responsibility of being a parent, but you should throw away your selfish card, because the day you became a parent that card should have disappeared without hesitation to keep it in your hand.
What should never matter is what situation you find yourself in:
Nuclear, single parent, extended family, same sex, stepfamily, adoptive, biracial, etc. please do not ever take offense to any situation I forgot to mention, because to me all that matters is the children who are under your roof, the children you influence, and the children you show your love and affection to.
It's simple, yet it's not, I do know this. Every time you want to bash the other parent, the other party, the parent who decided it was not for them, just remember them; remember the child/children without a voice, the child who didn't have a choice......the child/children. It's simple, yet complex, but no matter what, you must always remember them and put them first.
I live in the single parent/stepfamily with my boys and it's hard; you will never hear anything different from me, but once you take "selfishness" out of the equation and focus on your kids you realize there are many people who would give anything to have even what you have.........many people would give anything for a moment with their kids, another birthday, to watch them graduate, to get married, etc, and sadly they don't have another moment with them. Some people, because of what they can/could control; others, because it was out of their control.
I'm looking at the parenting side of this, but step back and look at the relationships in your life and think about this:
"Love is what is left in a relationship after all the selfishness is taken out." Cullen Hightower