If you want to become a better athlete, it is important that you set goals for yourself. It's important that you challenge yourself to achieve those goals. You might not be able to do this every day, but you should definitely do something once a week that pushes you - whether this is physically or mentally.
Hill training is a great way to push yourself. If you try to run faster every time, you will always be pushing yourself. This is a great physical and mental exercise and so is a fitting video to finish this series.