Have you ever tried to understand a 2 year old? One of the blessings (and difficulty) of being a grandma is that I love hearing my 2 year-old grand daughter speak to me. She rambles on and on about "Elsa and Anna," but the words in-between get lost in translation. This is a stage in their young life when parents want to teach their children the value of sharing with others and discourage their being "selfish" or as my granddaughter says,"shell fish."
I often talk to clients about codependent behavioral patterns that can lead to one person caring so much for the people, places, and things in their lives that there is no time (or energy) left over for themselves. They press on in survival mode seeking ways to do for others so they can feel appreciated, loved, and accepted. Unfortunately, they learn after years of giving that they've run out of energy, are discouraged, depressed, and have deep feelings of resentment toward the same people they've been desperately trying to please. So, I tell them to "be selfish." They often give me all sorts of excuses why that would be "bad," "selfish," and they "just couldn't" because that's not who they are.
You have a cup which contains energy, love, and generosity. The cup has limits to how much of these components you can possess. Now imagine that you are "pouring" out of your cup into the cups of your children, your parents, your spouse, your coworkers, your boss, your job, and your church. Eventually, you will come to the end of yourself, and your cup will be empty. At that point, you'll realize how little people are giving to you. You will want them to pour into your cup, but they have become so accustomed to you doing the pouring, that they will resent you for expecting they do any anything for you.
In the book, Take Your Life Back, Stephen Arterburn, M.Ed. and David Stoop, Ph.D. discuss the difference between self-centeredness and "self-care," and why doing something positive for ourselves can feel negative,"It's important to remember--or to realize--that our woundedness has made us think that any self-care we do is a selfish act." To do something nurturing for ourselves is not an act of selfishness, it is a healthy way of giving to yourself.
So, whatever it is that you consider selfish reconsider if it's really self-care. Do some healthy shell fishing and fill your cup. Then you'll be able to GIVE, without resentment, from a full cup.