pinky, when I was about 20 years old, I had a friend who was roughly the same age as me, but much more worldly, and he explained to me that if you have a credit card and pay off the debt at the end of each month, that's how you build up a good credit rating.
I really don't know much about personal finance, though. Anything else about money you've learned recently, that you should've known in your 20s, or possibly earlier?
I knew that part. Here were the parts that I learned since then:
Don't borrow money you don't have, unless it's for something you need and/or something that will reliably generate wealth or reduce costs. E.g. don't finance your furniture or a car beyond your means. Do get a mortgage, maybe.
Never justify buying things on finance based on being able to keep up with the monthly repayments. If you have to finance something, only justify it based on how much you are prepared to lose and how quickly you can have equity.
Don't buy things on your credit card unless you can pay off the full balance each month. Don't fall into the trap of leaving some leftover for the next month and justifying the interest. This is the slippery slope that leaves even smart and sensible people into mountains of debt.
There is literally no cost effective way to buy a car. The least shitty way is to buy it outright with cash. A car should cost no more than 10% of your annual income, generally.
Add another 10% for general car costs.
If you really want something you can't afford and you're thinking about putting it on a 2-3 year finance agreement, think about how emotionally attached you are going to feel about it in 6 months time, and consequentially how bitter you're going to feel about those repayments once the novelty has worn off.
Set aside a monthly budget for annual costs. If your car's accident and emergency costs 150 a year, then set aside 12.50 a month for it. That payment won't sting at all when it renews next year.
Keep 3 months of salary in savings as an emergency fund. You don't touch this for holidays or toys or whatever. This is just there in case you lose your job and you need that cash there to keep you afloat.
Finally, maybe live your life a little anyway. Certainly being financially covered is important, but no one sits on their deathbed and remembers their investment portfolio.