The $SPX is tracking toward a fourth consecutive red day — potentially closing at levels we haven't seen since July.

Four-day losing streaks aren't rare, but they do tend to sharpen focus. Market's had a solid run, and pullbacks to summer levels can feel dramatic even when they're just normal digestion.

Worth watching: whether this is profit-taking after a strong year or something with more teeth. Either way, perspective matters — July wasn't that long ago, and the index was doing fine then too.