Taking responsibility for inner dialog is the key.

As for what actually "works", one measure is not whether one produces journal entries (however insightful), but how journalling helps with minding one's life -- in the same way that anticipating a dialog with a therapist or friend might lead one to temper one's own dialog (or conversely, how worrying about what people think might be inhibiting).

I do think that imagining oneself in a constant dialog with Socrates could be illuminating.

Some interlocutors are direct, correcting faults or encouraging you. But the best teachers use indirection, setting you a challenge that should break you of a bad habit or push you to realize a mistake or integrate some insight (Nietzsche intimated that enemies can be better than friends in this regard). People who posit that everything happens for a reason (or, as Thales said, the world is intelligible) do a reflexive form of this, challenging themselves to find that insight or truth.

Similarly, some interlocutors are careful to not inject their own positive bias, but eager to protect against errors; e.g., "the unexamined life is not worth living" says little about what kind of examination helps. That creates essential space for one's own agency.

Ultimately, you create your world, even if you have no choice, so be at least as kind and forgiving as you are critical and diligent.

Your point about balancing criticism with kindness is the key takeaway. Agreed!