It's pretty easy to make the wrong choices at a critical moment and end up with the bad ending but the game tells you in advance basically "SAVE YOUR GAME RIGHT NOW!!!!" so you can easily reload and try again.
Other than that, you can play completely without a guide. I had never played a Persona game before and I found it very easy to figure out and get into. I'd actually recommend not using a guide since the game will have more of a sim feeling to it.