It’s another one of those catch 22 situations, since if you start where you think your novel should ultimately start, you might find yourself having to write beginning chapters after the novels written, because you find you need those chapters to make you novel to make sense to your reader right from the start. So is it better to start earlier in the story, and find you should cut out a few chapters or to have to write those preliminary chapters after the novels written?
For me it makes sense to write where your head is telling you to start your story during the rough draft of the novel and see where the chips fall once the novels written. Even if those first few chapters end out in the trash heap in the final draft, since it gives an opportunity to learn valuable information about your main characters and maybe ultimately give yourself good stuff to work into the final draft of the novel, even if it’s just little flashbacks or solid back story to build into the novel through richer conversations amongst your characters.
In the long run it’s up to the individual taste of the person writing the novel. And I’m going to go about it my way and not worry too much about my mentor worrying about me getting to the heart of the novel, since I know I’ll figure out a way how to get there from how I feel the story should begin right now. I just have a lot to show my potential readers about how and why things need to move the way they do in this novel and I can’t compromise on that vision. At least not at this moment.