Heart of the Woods has a somewhat strange way that it handles options, and it reflects in a potentially confusing flowchart. The short version is that if you want access to all three endings on one playthrough, choose "I should let her mourn." and "She'll pay for this." OR "I have to keep her strong." and "There's nothing we can do."

The long version is actually only a bit more complicated. The first option ultimately has very little impact on what options you get later on, and affects minimal dialogue. Guides that state a specific first option must be chosen for a good ending, from personal testing, are incorrect. Most options in this novel only result in a small scene directly after and then with the endings you can choose. The option that does have consequence on your ending options is the second option and then the third option.

Choosing the opposite second option path such as "I should let her mourn." and "There's nothing we can do." will result in being locked into two choices of "One way or another, it ends tonight." and "I'll keep Tara safe." Ironically, choosing the opposite second option path will always culminate in the same bad ending as both choices lead to the same bad ending with little difference.
This means that choosing the incorrect second choice locks the player off not only from the Good ending, but also the second Bad ending.

The three choices (Provided you've chosen a correct second option path) at the final chapter all essentially reflect which ending you're choosing. I recommend creating a save at the exact point of the choice as all three endings provide extra content to read through, and are the one case where a different choice results in a significant amount of content.

If I've gotten something incorrect (per personal experience with the novel OR a content update), please leave a comment!