"It is a sore point, because you do have advantages if you have access to more than one language. You also have problems, because on bad days you don't trust yourself, either in your first or your second language, and so you feel like a complete halfwit"

In this quote, the speaker is going over the intricacies and challenges of being multilingual. They acknowledge that having access to multiple languages can be beneficial, however likewise explain that it can also bring about troubles. The speaker mentions that on "bad days", they may battle with self-doubt and seem like they are not proficient in either their very first or second language. This can result in sensations of inadequacy and frustration. Using the expression "complete halfwit" stresses the speaker's sense of being insufficient or doing not have in some way. Overall, the quote highlights the intricacies and struggles of navigating multiple languages and the effect it can have on one's self-perception.