You can do it! Just realize that it with take a couple of years of practice and just move along with new things (and more challenging trimmings) at your own pace and comfort level. Stay friends with your farrier and keep watching and learning. There are a few good books out there, too!
I did the same thing you were doing at age 14. Here I am over 20 years later and I'm always the one putting pulled/lost shoes on horses with friends at trail rides, but I do not shoe for money and neither do I shoe other peoples horses other than what I mentioned above. I swear them to secrecy because I have no desire to become the camp farrier on a weekend getaway in the hills.
I only trimmed for years and years and only over the last decade or so learned to shoe. I had horses with navicular issues and learned from a WONDERFUL guy who was my farrier for two years how to trim and shoe for natural balance shoes, synthetic and shoes with wedges. Of course regular shoes as well.
If I can do this, you can too! Keep going at it and don't give up. What a great skill to have. Plus it gives you great biceps and upper body toning. Nothing wrong with that!