My native tongue is English, but I also can speak Spanish pretty fluently. My only issue with that is that I need to strengthen my vocabulary. You can learn to speak a language in a multitude of different ways: you learn your first language just from being exposed to it in your every day life with some reinforcement in school(the most basic method) or another good way is to learn the very workings of the language itself. If you seek to understand the mechanics of the language, it will make constructing fluid sentences and paragraphs all the more easy. There is a lot to consider in a language such as: how they construct their verbs in all the conjugations, how they deal with noun and pronoun placement, how to use direct object pronouns and indirect object pronouns, you need to learn the alphabet and how to pronounce the letters as well as be able to speak in a variety of tenses including but not limited to: present, past progressive, past imperfective, perfective past, and future tense depending on what language you wish to learn. It is by learning these concepts that you make the step from learning the language to speaking the language. It is no doubt going to differentiate with the language, but is these basic mechanics of all languages that can be applied to learning all languages. When you begin to look at how you construct the language from the necessary parts(what you read or need to say) by using the proper tools(the concepts to consider above) it becomes shockingly clear and simple.
I can't vouch for the effectiveness of Rosetta Stone and similar products... but I personally believe that they would be a waste of money. They aren't going to teach you anything that you can't teach yourself. Learning a language is easy, but it requires legitimate thought and actual dedication. You must constantly instill the concepts in your brain and practice them. You must become comfortable with working words in a different manner than how you have your whole life; you must do while not forgetting how you originally do so in the first place. If you just think about the language you are trying to learn, it is sort of like a puzzle. You have all the pieces to construct beautiful , fluent speech, you just have to figure out how they all fit together. But better than randomly trying pieces in a mundane, ineffective hit-and-miss routine it is best to develop methods on how to recognize what pieces fit where.
I see nothing wrong with learning another language just because you want to. Especially not if you love words as much as me! Granted it is more beneficial to actually learn a language that could be of.. well, benefit, but nonetheless: The more languages you learn, the easier it will become to learn other languages as they often connect to each other through borrowed roots and words. While they indeed their own independent languages, they were spawned from similar origins, a common ancestor, from other languages that share their same characteristics. It is through a process of divergent evolution that the languages have the ability to grow so distinct yet at the same time retain their core identity.
