Since playing an instrument since the sixth grade, and singing since I can remember, I never really actively practiced and it showed. Sure, I had a fun time and thought I was pretty decent, but I never really improved after high school ended. At least, not by a whole lot. I played scales, okay, but I never was really confident in knowing them by heart.
My tone was atrocious, I didn't know what to do to get better. I thought I was too good to practice, although, some things were too easy for me to practice at the time. Still, I could have practiced something. I literally didn't get myself anywhere by thinking I was good.
Playing/singing music in college is so much different than playing/singing in high school. The pieces are hard, the amount of energy it takes to get through one piece is so much sometimes, and it can get mentally exhausting.
And without practicing, it felt impossible to play. In my voice lessons, I was not improving and I could not figure out why. I didn't think I needed to practice. Only people who need extra work needed practice.
That is honestly what I had thought for years. I now realize how ridiculous that is and how immature I was then as a person and as a musician.
But I learned that it's good to practice! Practicing is good and it helps so much. Keep running that through your mind. Don't forget it. Start a practicing schedule! Even just thirty minutes, you'll be surprised at the outcome!
Five hours a week is a great start, but start slow and don't overload yourself. And start early. Don't wait until college to start! Tackle it head on and watch yourself become a better musician.