Problem, you can’t become a guitar virtuoso … You are, or you’re not. A human body is not a machine: with a few exceptions, your body would be completely worn out after 10 years of intensive guitar practice. If you really have to practice 12 hours a day to be able to play guitar well, you probably have insufficient aptitude for this instrument.
A guitar virtuoso is someone with a naturally exceptional and extreme aptitude for something. These people do not have to practice for hours a day to be able to do that “something”. Playing music is not a competition. So, practice at your leisure and put more emphasis on playing music than playing guitar for hours. For example, a touring musician is already very happy if he can practice guitar for an hour a day …