Riddle -- What is it?

If you have it, you don't need it.  If you need it, you don't have it.  If you have it, you don't need less of it, you need more of it.  But if you don't have any of it to begin with, then you don't know how to get any of it in the first place, now do you?  You can share it, sure.  Stockpile it if you like.  But you can't fake it.  Wanting it, needing it, wishing for it.  The bottom line is, if you don't have any of it, people just seem to know.

Oxygen?

Good answer, but if you have it, you don't need less of it, you need more of it.  Doesn't quite work with Oxygen, because you can get too much of it and need less of it.

happiness!

sex

Nothing.

Money.

Keep guessing

love

The answer is . . . . TIME.

not sure how you stockpile it, though.  there seem to be a few issues with each answer. 

of course, the riddle seems to contradict itself a bit.  if you have it you don't need it, but you may need more of it.  so, apparently, just because you have it, you may also need more of it.  shrug. 

I think sex works just as well.

for most problems, really.  i mean there are a number of US idioms to support this theory. 

Ok, if it's not Time or Money . . .  it must be Patience.

Can you stockpile patience?  I often find myself running out of it.

Food?

i am now voting for stupidity.  all of us who are still thinking about this riddle, obviously need less of it. 

I would guess that it is experience.  Either that or "Old Spice" products.  Are you a Bruce Campbell fan too?

First you want to kill me. Now you want to kiss me. Look at my hand. Now look at your hand. Now back at my hand. My hand is now a chainsaw. Look at my other hand. Groovy. I have it. It’s a shotgun. Look again. The shotgun is now a sawn-off. Look around you. Now look around me. I’m surrounded by deadites. Look at my chin. It’s awsome. Look around me again. The deadites are now dead. Anything is possible when you’re Bruce Campbell wearing old spice. Come Get Some!