She's impulsive and often does things that she later regrets.
He needs to learn to control his impulsive behavior.
She made an impulsive decision to quit her job.
I couldn't make out exactly what had happened, though I could guess how it started—the two of them talking, kidding around when Mrs. Ramsey came down to the library basement to file some periodicals, an impulsive kiss in the stacks … —Tobias Wolff, Old School, 2003
There was an odd nobility, a knight-errant quality, about Alan—in his willingness to suffer for the sake of life itself, in his tendency to view himself under harsher light than he would turn on others, in his impulsive generosity. —Tracy Kidder, Home Town, 1999
So speaks Maude Bailey, the celibate feminist scholar heroine of A. S. Byatt's fifth novel, as, in an impulsive collusion with a male scholar she scarcely knows, she runs off to Brittany. —Joyce Carol Oates, Vogue, November 1990