It depends. Sometimes the praise can be helpful. Something like, "Your story is very good! I really liked how you [insert] and how you included the [insert], it really showed that you [insert]!" That is good praise. I don't like the type of praise that goes, "Wow! Your story is really good! Goodbye!" That's not helpful, and it's not even praise to me, because it just sounds like they are in a rush and they really do not care.
Now criticism on the other hand. It depends, too. Mean criticism can be very hurtful. Like this: "Your story seriously sucks. You had no [insert], and your [insert] was so poorly written, you will never succeed, just give up right now because you have no talent." That is mean and hurtful, and not encouraging at all. Criticism is supposed to help people. Not discourage them. But constructive criticism is very, very valuable. Like this: "I really think you should improve on [insert] because your [insert] wasn't the best, but I think if you really try to [insert] then you will get better at [insert]." Now that is very good criticism. But the last type of criticism is particularly bad. It's worse than mean criticism. It goes like this: "Your story sucks. Bye." That is hurtful, and mean, and pathetic, and it hurts even more than the first type of criticism, because they are saying that your writing is bad, and they are also saying how they really couldn't care less to explain WHY it was bad.
So it really depends on the giver of the criticism, and how they deliver it.