Caffeine is a popular substance that can give anybody a quick fix. With it, you will feel an increased stamina as well as enhanced endurance, especially if you have a very busy day. Also, caffeine is a mood lifter, and this will work wonders for people who are very stressed out on their jobs. As such, caffeine pills are very popular to students who require long hours to study. Caffeine pills are also taken by people who are always on the road and are driving for long periods of time.