I've had this go both ways before, too. I think the point to take away from this sort of experience is that the best you can do is apply your best judgment and

I've had this go both ways before, too. I think the point to take away from this sort of experience is that the best you can do is apply your best judgment and re-evaluate as you go along. Often opaque documentation makes sense after you gain some context by reading the source; it works the other way, too. With experience, you gain a sense for what path to go down; sometimes that (subconscious) heuristic is totally wrong, which is why it's important to consciously re-evaluate on top of that. The current approach isn't making you any practical headway, even though you're learning a lot about the system in question? Take a step back and try looking at the bigger picture; what are you really missing? If you can, sleep on it for a bit. Most of all, if you're getting it right more than 50% of the time (and I'm finding it hard to imagine a way you'd do worse than that) there really is no point beating yourself up about it.