The best way I've found to identify vocabulary most important to my life is through journaling in the language I'm trying to learn. Describing exactly what I did that day, my thoughts, etc, as best I can.
I had thought of doing the journal entries digitally and gathering dictionary headwords from such journal entries, whether they're written in my mother tongue (English) or not, and use the built dictionary lists to drill vocab.
Traditionally you'd use a lemmatizer with a morphosyntactic tagger for the language to identify the dictionary words, but AI is serviceable these days to easily identify dictionary words from long-form text in many languages, though honestly would be surprised if AI outperforms the traditional methods already.
Good luck and have fun :)