Its happend to me alot and it is very scarey becuase they could send you flying but they always stop dead in front of you,i you feel really scared try turning you back to them and standing still,or makin you way to the nearest fence,if you have a lead rope in your hands try swinging it arounda little just to warn them to back off.  . . but other than that i wouldnt worry,Hope i helped

To be honest, I am positive that most horses gallop towards you to say "hello" or to see if you have food and would stop before actually getting to you.  In that situation, it is best to stand still and let them get to you as they will judge when they need to slop down etc.

But you could go and stand by a fence, which they would have to slow down for (hopefully!)