I haven't had money problems since I started my 2nd job when I was 19. It's been almost 10 years since then and I haven't been close to running my savings down since. I'm cheap and before I would make a purchase I would think "Do I really need this? Will the happiness I get from it outweigh the price?". If yes, then I'd go ahead and buy it and enjoy it. If not, I'd pass and just keep saving my money until something good really caught my eye. This allowed me to save up money and then I could waste it on food or entertainment from time to time without worrying for a second about my budget.
The single biggest thing people in their late teens and 20's waste their money on is a car payment. Society has tricked you into believing you're a piece of shit if you don't own a new ride. I bought an older car and did research online when it came to working on it. I did 95% of the repairs myself and saved thousands of dollars by not only maintaining my own cheap vehicle, but only paying for liability insurance as well. All my friends who bought their vehicles new are living at home with their parents or with multiple roommates. One friend had a new truck but after he wrecked it, he used the money to buy an older car and paid off his debt. He now owns a house. I drove my old car for years and saved up my money. I now own a house, an extra project car and I'll be buying another house in a few years.
I'm no financial expert but here is my advice. Never, ever spend money you don't have. Don't ever spend money you expect to have. If you don't need it, don't buy it. If you don't have money at the end of the month, start making cuts until you do. Make your small purchases with a credit card and pay them off at the end of each week to build credit. Quit acting like you can't live without your smart phone with unlimited everything. Either have internet on your phone or have it at home but you don't need both. If your cable bill is too high, start using the internet for TV. Sign up for cheaper gas, water and electric. Most companies have a program for this if you don't make much money. Eat lots of grilled chicken and frozen vegetables. Not only are they cheap, but they're good for you. Once you build up $2000 in savings, that is now your poverty line. Never dip below $2000, no matter what. Hopefully the things you've learned will keep your savings piling up while you're still able to go out and buy the things you want and do the things you want to do without worrying about whether or not you can afford it.