You will not develop it by choice, keep it under control, use it to your advantage like a diet, and get the body you want. You will be absorbed by it, it will control your thoughts and actions, it will ruin your health, and turn you into something you never wanted to be. It is not a trend or a habit you can pick up and then quit when you feel like it.
It's not convenient. It's horrifying.
You see all these images online of girls in cute leggings and boys in skinny jeans. You think, when I'm skinny, I'll be able to pull that off. You forget that with the thigh gap comes dizziness and fainting and bruises. You think it won't happen to you. You think if you keep eating your vegetables it won't matter that you're only eating two servings a day. It still matters.
Restricting will make you nervous and jumpy. Binging will make your stomach hurt. Trying to purge will make your throat ache. You'll end up regretting every decision you make regarding food, no matter what direction you try to go in. Repeating the cycle won't make you feel better. When purging fails, exercising on an empty stomach will leave you embarrassed at the gym, because you're cold-sweating and lost your balance on the treadmill.
When you get to the point you can't exercise anymore because a flight of stairs exhausts you, it won't be fun or pretty. Wanting to die because you set goals you'll never accomplish isn't cute or glamorous. This is why I worry when people say things like "I wish I could just forget to eat", or they think disordered eating is some measure of willpower. It doesn't make you stronger. No one is going to applaud your determination.
The only trophy an eating disorder is going to win for you is your coffin.