Over time, and looking at hundreds of setups, my brain can now start to spot whether a pattern is valid or not. I can't always fully explain why a setup is valid or not, but after a while it's just a case of looking at it and going 'yes' or 'no'. And if it's a 'maybe', then I don't take it.
IMHO, using our brains in this manner is one advantage that we have over algos in that it might be difficult to program these human brain processes. At least more difficult than scanning through dozens of black&white checks in order to execute a trade in a millisecond.