You are doing the wrong thing about investing. It is not important to have a discretionary income before investing in Bitcoin . If you are studying in a university, you will learn about Bitcoin and you can accumulate Bitcoin during your studies. Buy Bitcoin by saving some money from your part time job or from the session fees you get from your family. You will gain knowledge about Bitcoin while you are a student and along with that, you can accumulate any fractional amount. It is always intelligent to rely on your own cash fund. If you take out a loan or depend on other people's money to invest, you will not be able to keep it going in the long term.
You need a discretionary income in order for you to invest into bitcoin and hodli for long. I understand what you mean, it's just that you don't understand what discretionary income is. Discretionary income is the extra money from your income that you can do away with and it wouldn't affect you lifestyle. Some people use it to drink, smoke, gamble, club and many more consumption al stuff. Using such funds to invest in bitcoin is the best because you can use it to grow and build your bitcoin portfolio for the future.
That is actually the smartest way to invest. Using discretionary income just makes everything easier because you’re not putting pressure on yourself or touching money meant for your basic needs. Most people make the mistake of investing with funds they can not afford to lose, and that is why they panic sell when the market dips.
But when you use extra cash, the one you would normally spend on flexing or random stuff, you can hodl longer and stay calm no matter what the market does. That is how real long term conviction is built..