I have trouble feeling assertiveness. In the meanwhile I learned definitions of what it is (they say you have to "stand up" for yourself, and then I picturize myself standing up from a chair), but I cannot feel the meaning of expressions like this. Meaning I am still who I am as shy and introvert (except sometimes talking about a field of interest) or "acting over" my shyness as I have always been, though I have read about these topics, but I cannot connect these phrases with a feeling.
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English is not my native language, so I will very likely do mistakes in writing or understanding. My edits are due to corrections of mistakes, which I sometimes recognize just after submitting a text.