I had the same thought. I'll quit after school. That turned into I won't dip at my office or during working hours. I think that lasted a day or two. Next up was that I would quit upon marriage. I got married, but didn't quit. Then my daughter was on the way and I declared to myself (not to my wife or anyone else, because down deep I knew I'd never quit) that I'd quit before she was born. I left wife and baby in the hospital to go hide and dip. My family would all wonder where I had been, but the lies were "necessary" because I needed a fix.
Don't listen to your brain right now. It's all fucked up with addict thinking and nicotine trying to convince you to have just one. If you've spent more than five hours reading on this site, you know there is no such thing as "just one." Folks who have been quit for 8 and 15 years are in here posting roll (TODAY) and having to endure this bullshit again because of "just one."
If I could cram what I know into your 19 year old head, nic wouldn't have a chance with you today. You'd get laid a whole bunch, too, of course.
Seriously, you not only CAN do this...you NEED to do this. Don't waste another second letting that shit control your life, take your money and be the doosh bag friend who won't leave.
Let's get it done. Yell if you need anything.