I missed this - body language experts the world over will tell you that body language is culturally and individually unique.
Some people share similar body language for displaying certain emotions, but they are not universal.
Further you may be able to tell what some people are feeling by their body language, but there will be many many more examples where you miss the emotion.
Worse, the ones that you can get an idea of, it's very VERY rare for you to know the reason that people are in that emotive state.
edit:
This even applies to people close to you, who you think that you know.
I'm saying intuition in a complex space we don't understand is less reliable than intuition in a simple well understood space.
Recognising that someone is angry is simpler than discovering how gravity works.
Science has a high failure rate and scientists heavily lean on their intuition.
This does not imply that it is intuition that causes the high failure rate.