The end of a year and the beginning of a new year is always a good time to assess things. The new year is just a date on the calendar, but for some reason people use it as a time to reflect and look forward. People make resolutions for the new year, but they could just as easily do this in the middle of July.
As far as resolutions, there is nothing wrong with them and you should do them if they work. However, you shouldn't put off to January things that should be done before then. Also, if a resolution consists of a good habit (like eating well or spending less), then this should be done year-round. It is better to form good habits with exceptions than bad habits with exceptions. It is better to eat well for most of the year but let yourself indulge during the holidays than it is to eat poorly for the year and then spend a couple of weeks in January trying out your resolution.
The end of the calendar year can be a good time to assess your situation in life and this includes your financial situation. It is a good time to figure our your net worth and where you can do better financially. You could just as easily do this in July or any other month, but will you remember to do it then? That is why the end of the year is a good time. You will be more likely to remember to do this exercise.
Take a piece of paper and write down your assets and liabilities. Take your year-end statements from any 401ks, IRAs, brokerage accounts, bank accounts, etc. Write down the amounts. If you have anything else, estimate the value and write down the amounts. Also, do this for your liabilities. If you have car debt, a mortgage, or any other debts, write them down. Figure out your net worth. If you do not rent, figure out two figures. Figure out your net worth with your house (minus your mortgage) and figure out your net worth without your house (also leave out any non-investments like cars or furniture).
After you do this, put this in a place where you can find it next year. It may be in a filing cabinet or you may want to put it on your computer. It will interest you to see what changes have taken place and if you are saving and investing the way you want.
In addition to this being a good exercise to seeing what you have done right and wrong, it is also good looking forward. You can see where you can do better. If you are not an active trader, it is also a good time to re-balance your portfolio. If you like to keep an equal amount of stocks, bonds, cash, and gold, and stocks have gone up significantly in the last year, it is a good time to sell some stocks and add this to an investment that had done poorly. Don't count on stocks to keep going up. Put your investments back into balance.
Again, you can do this any time of year, but you will more likely remember to do this at the end of the year. You weigh yourself to see where you stand. Do the same for your finances and step on the scale.