Yup, I sure have. After my first year or year and a half at uni, I decided to start over again because I didn’t feel like I had done my best (I’d spent my time on Android development). In other words, I had decided to take the courses once again. That was absolutely horrible, and really demotivating. My situation didn’t really improve much. At one point, I decided to ignore school for half a year and just focus on Android development.
The best way to ensure that you’re motivated is to find a project that you’re really excited about. Find something you’re using daily and try to make it better, one step at a time.