Who said "Gratitude is a sign of strength."?

This quote is attributed to Nebula.

Gratitude is a sign of strength. - Nebula

"Gratitude is a sign of strength."

Nebula Gratitude

"I didn't ask for this life."

"You're welcome."

"I will kill you slowly."

"Gamora may have stolen your money, but I will steal your life."

"Gratitude makes life richer."

"A grateful heart is a happy heart."

"Respect those who came before us."

"Life's greatest treasures are the people we love"