Catching forty winks is often used as an idiom for taking a short nap during the day. However, if you want to express the opposite meaning, you can use antonyms such as staying alert or staying awake. Instead of snoozing or dozing off, you can try engaging in physical activities, drinking a caffeinated beverage, or keeping your mind active to stay awake. If you'd like to use a more emphatic antonym, you can use phrases such as 'burning the midnight oil' or 'pulling an all-nighter' to convey staying up all night to study or work on a project. Regardless of the term you choose, it's essential to prioritize your health by getting enough rest each day.