In English or Chinese, components of a sentence is decided by its location. For example, both English and Chinese belong to a S+O+V language and the order of components is changed in a sentence, its meaning is also changed or even becomes incomprehensible. 1) I love you.(我爱你。) I = subject, you = object 2) You love me. (你爱我。) Now, "You" became a subject as it is placed in front of the sentence and it has a totally opposite meaning. 3) Love I you or Love you I. We cannot get what this means. On the contrary, the components (case) is decided by a case particles like "이, 가" (subject) or "을, 를" (object) in the Korean language. Therefore, we can understand a sentence even though we mixed up the location of each component. 1) 나는 너를 사랑한다. (I love you.) => This is a normal order of components in Korean. 2) 너를 나는 사랑한다. (I love you.) Here, the object came first in the position of a subject but its meaning is still the same as 1) because we understand "너" is an object because of the case particle "를" no matter where is placed. 3) 사랑한다 너를 나는 (I love you.) This sentence is apparently ungrammatical but there still is no problem for Koreans to understand its meaning. I hope you can understand how important "particles" are in the Korean language.

@Mojave: ow I see! okay! it's just really hard to become familiar with those particles. -_-

As far as I know, you never drop location particles. As for the others, I think it's best to stick with strict grammar. It's a lot easier to learn it correctly first, then drop later, rather than to not know how to use them later. Most native Koreans on italki will correct your questions and journal entries by adding particles.