What does that refer to in the passage? Doing(Trying) what worked for your friend, or guessing and chance, or another? I think that refers to the latter because it encompasses the other two Wrong ways before the the one extracted from the source.
Wrong way #3:Doing what worked for a friend Advice from a friend or family member is the most well-meaning of all, but it’s not the best way to match yourself with a new habit. While hot yoga may have changed your friend’s life, does that mean it’s the right practice for you? We all have friends who swear their new habit of getting up at 4:30 a.m. changed their lives and that we have to do it. I don’t doubt that getting up super early changes people’s lives, sometimes in good ways and sometimes not. But be cautious: You don’t know if this habit will actually make your life better, especially if it means you get less sleep. So yes, you can try what worked for your friend, but don’t beat yourself up if your friend’s answer doesn’t change you in the same way.
All of these approaches involve guessing and chance. And that’s not a good way to strive for change in your life.