- Inner development: common but development has some unfortunate connotations
- Inner growth: has less of that development edge. warmer. however, has the "growth" implication there.
- Ontogenesis: the most accurate. Also can be paired with culturogenesis. however, is obviously obscure and off-putting for that reason.
- Cultivating inner capacities: the most nuanced yet still accessible phrasing. Nevertheless less familiar than inner development etc.
NB: James Mark Baldwin and co use ontogenesis quite a bit 🙂 However, this is late 19th century academic psychology and it has definitely fallen out of fashion.
NB: ontogenesis actually used more than inner development, at least according to google ngrams (though that is only books …)