I think this may be something that really depends on the person. English is my native language but I also speak Mandarin and Japanese at around an intermediate level. There are certain words and letters I get blocks on in English but not in my secondary languages. For example, words that start with W have always given me trouble in English but in Mandarin they don't. Something like "**w**hat are you doing in today?" would be difficult to say but "**w**ô hùi shuö" (mandarin for 'I can speak') is effortless.