Sounds as it sounds, you have to learn it.
Some teachers have named the subjunctive -"the wolf´s ears"- because it´s the first time that the student of spanish as a foreign language get a little bit scared. Not all the languages havethis grammatical rule.
But you have to know that Spanish has three verbal modes, the indicative, yhe conditional, and the subjunctive.
The indicative is used to outline (indicate) something objective or true from speaker´s point of view and connected with what its referred to.
The potential or conditional mode refers, from the speaker´s perspective, to the a future or past action, to an unreal fact as long as they are demonstrable or possible facts, either independent or with verbs that depend on the main verb.
The subjunctive. it´s usued almost always after a structure or a verb. So, in very rare occasions it can be found only in a sentence. if doesn´t express necessarily in real time, but the conception and idea that the speaker wants to show.
The subjunctive it´s used independently with nosotros, nosotras, usted and ustedes of the Affirmative imperative and for all the negative and for all the negative imperative forms. Also with the reduplicative sentence (sea quien sea, lo haga como lo haga)
You use the present subjunctive generally to express doubts, hypothesis, value judgments, no established facts. It also expresses orders, prohibition, probability, wishes, fears, politeness.
And now we present you a short list of examples of the possible uses of the subjunctive:
1) to express doubts and probabilities or observations (quizás, tal vez, puede que, es probable que se hayan ido)
2) to express desire, need or hope (¡qué aproveche!/ ¿qué descanses!)
3) to express feelings (me gusta que seáis...; tengo miedo a que me echen)
4) to value actions or situations (es bueno/ malo/ lógico que ganen)
5)behind sentences with verbs and expressions that express advice, order, suggestion (permíteme que le recomiende el marisco; más vale que ahorrespara este verano)
6) to express permission, duty, request or to apologise (le ruego que no fume)
7) for sentences in the negative form (no creo que venga)
8) with expressins of falseness in positive, negative and interrogatives (es falso/ es dudoso/ es mentira)
We hope that this short introduction of the subjunctive helped you and keep in mind that in our special courses we will talk about this subject in detail ande when you will finish the course, you will perfectly know what the subjunctive is, when and how to use it and you will you will be able to show the use of it to any person that asks for your help.