Discovered triathlon

Welcome. I began triathlon at 59. One of the things I like about it is that age is no barrier to participation. It can be "meh" during the training days, especially the early ones, but you will feel a wonderful sense of accomplishment and joy when you cross your first finish line.
Have fun.

Tom,
I am a few years younger than you (18) and recently started training recently myself. Now I might be 32 (spring chicken, young buck) but I have had my fair share of broken bones and set backs in life. Remember what you are training for hours of physical stress. Your body needs fuel. Granted part of your health factors might be your diet, but a good strong diet and rest might make the difference between your blah days and your awesome days. Rest days could be very helpful, but don't sit on he couch. Take a walk, use a foam roller a couple times a day. Stick with it. Remember the end result, finishing a triathlon!