The person keeping a spending record is giving future memory less room to invent explanations.

Memory is a storyteller before it is a record. Left to itself it will produce a version of the month that fits the person you would prefer to be. A written record is not moral improvement; it simply takes away the room in which those explanations get made. What you are left with is the plain shape of where things actually went.

Try a week of writing it down with no judgement attached, not even privately. At the end, read it once without deciding anything. Deciding is easier when the facts have stopped being negotiable.