What should I do if I finished all my confidants in December?

I’m currently on December 5th and I just finished all my confidants and just beated Shido (may not be last which no spoilers). but because I don’t know what to do in the meantime are some things I should do to spend my time? so far I unlocked the required steps for the true ending as well so do I just grind or do something that increases HP?