We all do our best when learning a language. Some people focus on grammar and some on pronunciation. There are a lot of hypothesises about acquiring a language, but as learners I don't think we use these hypothsises as linguistics put them forward. We are normal people and we think logically. We justify what we do, but that doesn't mean that the way we use to learn a language's true.
We have one soul, but many personalities. For instance, I'm Arabic native speaker and I was raised by my real parents. What if I was raised by English parents not my real ones? I would've had no idea about Arabic language or even culture. That what happens when we try to learn English as a second language. We have to start from the beginning, however there will be differences. We can't learn English as we did in our mother tongue. Because we get scared ,lose self-confidnece and shy some times. Why all these happen to us? because we are grown up, think differently and have memories. Memories are full of happiness and sadness. We have experiences that effect on us.
First of all, we need to choose. Imagine yourself going shopping. You want to find the personality that suits you. When you feel that this accent's your cup of tea then, start learning it and not just the pronunciation. Learn the melody, stress and the way natives react to things...etc. It's going to be your sub-personality.If you prefer the British accent then go to the UK...etc. I wanted to share this with you because I watch and listen to my friends speaking in English and they try to talk like Americans. Although they created their American personality they studied English language in Newzealand or Australia. I know we live in a modern world and we have communications and I don't go for anyone, but it was easier for them to go to america.
The bottom line's that a laguage's more than collocations or idioms...etc. We have to live the laguage we learn till we make it part of us.