Many of you see me on daily basis;
I can be taken pure or mixed.
Some people say I prevent them from things,
others claim the opposite.
The small don't seem to like me a lot,
the big ones do sometimes prefer me over anything.
Who / What Am I?
(This riddle might be way too easy, it's just something that popped into my head and I thought it I might share it anyways ;)
After receiving so many different (viable) answers, this question might be considered too broad. To make it more clear, the title is another hint towards the correct answer. (Maybe it's not known that much, but at least I heard the answer being considered as the "essence of life" quite often.)