I know you're only 18 years old and you have time to think about and experiment with different ways to deal with quitting, but from a smoking perspective, I can tell you that you'll thank yourself for stopping right now. It's true. Ask anybody here. Come on, just do it - you're here on the forum, right... We got your back. What I'm gonna say here is just geared to help you...
Here's what you can do: Think of one of your girlfriends that you think is cool and that doesn't smoke. Just see how she acts without smoking. You'll want to, of course, not start anything else to replace smoking that could cause just as much trouble as smoking does. I'm sure you're a smart girl... But, back to what I'm saying.
My point is: Figure out what you would like yourself to be like if you had 5 million dollars - a massive beach house in Malibu, school taken care of, trips to scuba dive in Tahiti, whatever... Now imagine, in that visual of yourself, if you'd want yourself then to be still battling with this "I am trying to quit smoking" stuff. For you ( along with your plan ), that means that when it gets down to 0 cigarettes per day, THAT's IT. Give it up completely because when you go out with your buddies havin' fun and you're down to 1 per week, you may have another that makes it 2 per week, or even 3, then back up to 1 per day, then only 2 per day, etc. I'm saying, humans and ciggies don't work that way - by a few per week.
Just take my word for it, when you're 25 ( looking back ) and say, "I'm glad I didn't keep smoking like all of my friends did", you'll thank yourself! Now, relax, just think about it, and deliberately control it like you're doing. You're doing good by kicking it with us - you're helping us too, even!.. So, visualize! Dream big, baby. Cut your losses with the smokes. Define your life, and let it rip California-style.