“He’s untrustworthy,” Amaram said.
“He keeps his word, so far as I know,” Dalinar said. “That is more than I can say for most.”
“He keeps his word because he never promises anything.”
– Brandon Sanderson, Words of Radiance
If you say you will do something and you do it then it will increase people’s trust in you. If you say you will do something and you don’t do it then their trust in you will decrease, no matter the excuses you have for not doing it. If you don’t promise anything to anyone then you will never break anyone’s trust but you will not create any long lasting relationships either.