Feeling tired can result from many common reasons such as not getting enough high-quality sleep, stress, nutrient deficiencies, or underlying health conditions. Other causes include poor diet, lack of regular exercise, dehydration, and medical problems like sleep apnea or anemia. Lifestyle factors such as caffeine or alcohol consumption and mental health issues like anxiety or depression can also contribute to fatigue. If tiredness is persistent, consulting a doctor for proper diagnosis and treatment is advisable.