Common pitfalls in a fitness regimen include setting unrealistic goals, neglecting nutrition, and insufficient rest. Individuals may become discouraged if progress is not as expected, leading to discontinuation of their routine. Skipping meals or engaging in fad diets can impair energy levels and performance. Furthermore, inadequate recovery can result in injuries and fatigue. It's essential to create a balanced plan that includes realistic milestones, proper nourishment, and ample rest to foster long-term success in achieving fitness objectives.