Like if you ram your head into the cupboard doors when you stand up (tall people have that problem) or when you smash your toe against the hard wooden bed (remember it is like childbirth except it doesn't go on for hours) or accidentally hit something with your hand.
I guess if you know the obstacles are there your body slows down so you aren't hurt as much.
Some Rush Limbaugh quotes :
"If Thomas Jefferson thought taxation without representation was bad, he should see how it is with representation."
"Most people's historical perspective begins with the day of their birth."
"There's a simple way to solve the crime problem: obey the law; punish those who do not."
"You know why there's a Second Amendment? In case the government fails to follow the first one."
hard (adj) 1 solid, firm, and resistant to pressure; not easily broken, bent, or pierced : a hard mattress | ground frozen hard as a rock. 2 requiring a great deal of endurance or physical or mental effort : stooping over all day was hard work | [with infinitive ] she found it hard to believe that he could be involved. 3 done with a great deal of force or strength : a hard blow to the head. 4 potent, powerful, or intense, in particular