Translation is an art. As such, although it is true that theory knowledge is important, what is crucial is to have a feel for it. Being proficient in a language does not make us good translators; having a Bachelor's or Master's degree in a specific foreign language does not make us good translators.
There are other necessary aspects in addition to mere knowledge of the language. One of them, for example, is the ability to localise the text being translated; localising a given text means rendering it as close as possible to the target audience, i.e. the audience to whom the text is addressed: language, idioms, references should be as natural as possible to the listener or reader of the text.
A literal translation is never enough. Which is why book-based learning alone is not enough: films, music, travelling and spending time in places where the language you are studying is spoken are key factors in enriching one's knowledge of said language and the culture behind it.
In Italy, for example, the cultural difference between people from the North (a bit cold, serious, rule-abiding) and the South (much more easy going, cheerful and welcoming) is enormous, and we are talking about the same country. Let alone when we compare two different countries!
Translating means constantly learning something new: whether it is an idiom, a technical term, an expression used only in a certain context. Translating means quenching your thirst for knowledge. Translating means constantly keeping your mind in training. Translating is all this and much more.
Continuous technology development allows us to have a multitude of tools at hand that can help us during a translation: machine translation, free online glossaries, computer-assisted translation (CAT) tools, the possibility of processing translation memories, etc. Such tools are certainly of help to translators, but none of them can replace the creativity and mind of the person who is translating: only theoretical knowledge combined with practical knowledge can result in a translation of the highest quality, leading to customer satisfaction.
My Latin professor used to say: „Studēre, studēre, studēre!”. I have never been a model student, but that little bit of experience can only make me say: „Study, read, travel!”.
The more information you acquire, the more you will keep your mind in training. A well-trained mind translates more effectively and creatively!