Oh, here's one more thought that I would say to myself at 18.
Do have a better appreciation of music outside of hard rock/heavy metal and find ways to discover music outside of WWE playing their songs. You can still love bands like Alter Bridge, Shinedown, Seether, Skillet, and Daughtry, but there's a huge world out there of good music and it's best to discover them now than 5 years down the line. Bands like Owl City, Zac Brown Band, Poets of the Fall, etc. are pretty good and there's going to be a up-and-comer named Ed Sheeran that's going to be a mega superstar, but still can write pretty good songs that one can relate to.
P.S. Get into Rush now than two years before their final tour.