It seems that the perfect example to illustrate this point is Nikki Haley's behavior and her statements at the UN [UNGA, UNSC]. She seems like that kind of a person who has suddenly been put in a very high position for which she isn't qualified, and in order to be taken seriously, she has artificially adopted a very harsh, rude, tough, and undiplomatic behavior [lest she be ridiculed for not knowing diplomacy or for being too "soft", and lest she lose her job because of this]. What she doesn't know is that she's rapidly spending her political capital. Soon everyone around her - Americans and non-Americans - will get desensitized to her repeated/repetitive rhetoric and after that she won't be taken seriously.
Putting up a fake tough face is very easy. It's being genuinely humorous, witty and diplomatic that's tough. She thoroughly lacks any of these.
