when you hear hoofbeats, think horses, not zebras.

It means that the most obvious answer is usually right.

 It helps us stick to the truth. 

. When I hear hoofbeats, horses. I always think horses. Even when I shouldn't.

Things are not always what they appear to be. 

They're often an indicator of something bigger going on, deep underneath.

 Symptoms. Red flags. Warning signs. Things we should pay attention to. Things we shouldn't ever ignore. Things that are bad. Things that could really hurt us. 

Things that it might be just too late to fix.