The most selfish one-letter word I can think of,
"I"
It comes out of our mouth every minute.
"I'm hungry."
Let's go out and eat, my stomach needs it.
"I like it when you hold me."
This is making me happy. Do it again.
"I love your smile."
Please only smile for me.
"I love you."
Be with me. Grow old with me. Marry me.
"I am sorry."
Maybe saying those words made you feel less guilty.
"I am not for you."
A polite way for telling me to go find another person.
"I don't love you."
No need for explanation. You just don't.