How to Pick Up the Right Pace for a Story

Pacing is dictated a little bit by genre for example as a general rule an urban fantasy novel might be faster paced than an epic fantasy novel. When i switched from adult fiction to young adult fiction i had to learn how to pick up the pacing of both my sentences and the pace at which the story unfolds like my editor told me i needed to get my kids off earth and into space way faster. so if faster isn't necessarily better than slower and vice versa how do you figure out the right pace for a story?