Follow the instructions in that book to a T if you want to keep the negative thoughts at bay.
I can guarantee you that it will be uncomfortable and difficult at first, but it pays out.
Focus on making it a habit, don't be discouraged when you fall off multiple times.
You don't necessarily need to read the whole book at once, it's ok to just read about the stages relevant to you at the moment (do not skip any of them). The important thing is that you start your practice asap.
Also, check out the subreddit with the same name, it's very helpful to immerse yourself in their community. It's a wonderful hobby if done with the correct mindset and instructions.
I also want to echo hotelbeneathground's sentiment. The probability that you will fall off at some point stands at 100%, I'm afraid. Don't beat yourself up over it when it happens, it's totally normal and expected.