As children we learnt the subjunctive as part of every day speech.Parents would often say the following: If I were you, then I would not do that. [ I am not you, however, so I use the subjunctive to express this hypothetical or counterfactual condition. Especially note that the modern usage If I was you is completely incorrect.] If only Mary were here, then she would speak up. [ Mary is not here, however, so the subjunctive expresses that fact appropriately. Again, If only she was has drifted into modern usage and should be avoided.] In classes, we would often say these things about our teachers: We should act as if he were watching. [ We doubt that he is watching or know that he is not.] It is as though she were here. [ We know she is not here, but it seems so. ]

Well, we learnt it by following good examples. Remember it's always a hypothetical action, AND that there are actually a number of grammar rules, including second and third conditionals. Etienne has given you a link to Present Subjunctive, and Jura has explained Past Subjunctive. Be aware that there's a fair amount of overlap between the patterns of Indicative and Subjunctive Moods, but where they do differ, they should never be confused. PS. Your sentence should have been, "I am always confusED ABOUT this grammar."

http://www.englishpage.com/minitutorials/subjunctive.html I think it might help you!