Each language learned makes the next one easier, because you are more detached from your native language, you have more knowledge about structure, about meta-language.
(Naiman & al. 1996: 25).
Naiman, N. Fröhlich, M. Stern, H. H. & Todesco, A. 1996. The Good Language Learner. Foreword by Christopher Brumfit. Cleveland/Philadelphia/Adelaide: Multilingual Matters.