The part your question is circling and has not quite reached: recording is not the habit. Reviewing is.
Three months of faithful recording that you have never acted on is three months of admin. The categories only matter because they feed a decision, and if there is no regular moment where a decision gets made, no structure will help.
So build the review before you rebuild the categories:
A fixed slot, weekly, ten minutes. Same time every week. Look at the eight numbers, ask whether anything surprises you, and if something does, decide one thing to change.
One monthly comparison against the previous month, and that is all.
No more than one change at a time. The point is not to optimise everything; it is that the numbers cause something to happen.
On starting again: do not re-categorise three months of history. It is a large amount of work for a report you have already decided is meaningless, and the temptation to do it is what stops people restarting at all. Draw a line, set up eight categories from today, and let the old data be old data.
If you want a baseline, spend twenty minutes roughly totalling the old months into your new eight. Approximate is fine. It is a comparison point, not accounting.