"Selfishness" is in the eye of the beholder.
Everyone shares something with others. I've yet to meet anyone who considered (themselves) to be "selfish".
Selfish is a negative label (people put on others) whom are not doing what (they) believe they should be doing which usually entails giving them what they want. It's important to look out for yourself in order to give your best.
Practical usually means being "realistic" and has nothing to do with selfish.
Attempting to get others to "change" is a selfish act.
Understanding when two people don't want the same things and deciding to move on is a practical act.
The first law of nature is self-preservation
Each of us gets to choose our own friends, lovers, and spouse.
Life is a (personal) journey
Each of us is responsible for our own happiness.
We say all the above statements over and over again and yet when we come across someone who actually lives their life according to them we label them as being "selfish". They should be more concerned about (our) happiness than their own. Logically that makes no sense!
Anger is the Mask that Hurt Wears
It causes us to be cynical about the world in general.