Toad. i see lots of children doing this, and they don't seem to be correctly advised, so as you say, the habit sets in.
without some attempt at ankling, you have less control of the bicycle, as you have experienced.
also you are not using so effectively various muscles, so the effort yields less reward.
perhaps experiment with different footware, and begin by slight increments, towards the correct position.
you could perhaps practice the movement while sitting up on a bed/ sofa with your legs straight out, supported. now try to stretch the back of your calf by pulling your toes up towards your body.
good luck.