Why should you track your expenses?
Many people don't know how much they are spending and what they are buying. It comes as a surprise for people that they spend so much money without even thinking it. Insurances, transportation, clothes, housing, hobbies, subscriptions, food etc. When you actually track all of the money you spend, you will easily see how your financial actions dictate your account balance. That is a crucial part when you are trying to became financially free. Most of the people in western countries save max 15%, but if you are aiming to achieve financial independence, that number should be at leat 50%. It is not even that hard, but you just have to be mindful about you expenses and reduce them whenever possible (without losing your quality of life).
Also, I know people who are even afraid to see their account balance, because they have spent too much money. You might have had the same feeling after a night-out when you wake up with a hangover and -100 $USD on your bank account.
It is easy to track daily expenses with modern technology
Some people use Excel to track their spending, but it is kind of an old way to do it. I like to use Monefy - an app for tracking your money. The data from the app can be synchronized to your Google Drive, which is a very good thing.
Monefy is simple and easy to use.
Other apps/sites to track your money are for example MINT and Personal Capital. These are good if you want to manage all of your wealth in one place.