When Samantha O’Brien first stepped into a boxing class at her building’s gym, she was met with overwhelming anxiety. The instructor’s loud and intimidating demeanor created a boot camp-like atmosphere, where falling behind meant everyone had to work harder. Ms. O’Brien, 36, left the class feeling discouraged, convinced she wouldn’t return. However, a few days later, her partner brought home some cannabis gummies, suggesting they might provide her with a burst of…