Oh don't get me started on deciphering cries. I have absolutely no idea. I just guess. I usually get it right quite quickly (thanks to maternal instinct, what would I do without you!)
But when it comes to overstimulation/too hot or cold/or any other less common things, I take ages and then feel so guilty after.
Don't guilt trip yourself. Your baby doesn't mind if you don't figure it out straight away or even at all. It's all part of being a baby, I'm quite sure they are somehow prepared for all this.