IF YOU DON'T USE IT, YOU LOSE IT
It is always important to remember that your language skills are something that is dynamic rather than static. It is very easy to assume that you can do an intensive English course and once you have achieved the level you were aiming for you can stop doing anything in the future. This is the wrong approach to have with languages.
I have had many students that have passed the Cambridge Advanced Exam and then have not used their English for a few years and when they start to speak again they find it very difficult. So, you need to consider your English skills like a machine that needs to be maintained and well-oiled.
Hope that helps!
Soy el director de Daniel Smith + Partners. Tengo más de 10 años de experiencia enseñando inglés a españoles.