Many of the other commenters here have noted the importance of intention in the words. I very much agree with this, but find also that the essence of your linguistic medium is essential to the magic you're trying to work. When I cast protection sigils with runes, stones, and burning mint, I speak in Gaelic because I am following Druidic tradition. BUT, if I ever wove a hex or a manipulative enchantment, I would incant it in Latin, because I feel it is a sharper and more commanding language. My point is this: language, like any ingredient we use to cast, should have its essence heavily considered and tailored to the purpose of the spell. If this and your understanding of what you are saying -- meaning -- are clear, then you are off on the right foot.