To say that someone is too big for one's boots is a fair description of how he behaved after the promotion.

Being too big for one's britches, she dismissed everyone's concerns and made decisions without consulting the team.

I scanned the nine-page report, muttered "too long; didn't read," and asked for a one-paragraph summary.

After the promotion he started acting too big for one's breeches, bossing everyone around despite his inexperience.

After his first attempt at drawing a complex mecha, everyone said he would be a hundred years too early to capture the emotional depth of the series.

If she continues to fly too close to the sun by ignoring safety protocols, she risks losing her license.

I don't mean to be rude, not to put too fine a point on it, but your report omits several crucial facts.

Even healthy habits can be harmful if taken to extremes; for instance, too much of a good thing like exercising without rest can lead to injury.

After years of neglecting his relationships, he finally realized that it's never too late to mend and began reaching out to apologize.

Last spring she wore too many hats at the small startup and eventually burned out.