I started out logging my sailing expenses, including assigning each expense to a certain category, but I quickly gave that up. See Posts 1-21 for the reasons, I understand them all.
I do however have a very limited budget allowed for this, my first sailboat. That is so I'll have enough money to buy the second sometime in the near future. So, everytime I think of spending money on the boat, I not only think about what it will cost me today, but also what I could buy with that money if I had invested it for 5 years. Then I ask myself which purchase will make me happier? I've averted quite a few purchases with this technique.
So, if you want to learn how to really use spreadsheets, learn how to do compound interest calculations (available and easy in Excel) and run them before you spend money.