@simonrobea15: Both are 25. Both make $8,000 a month. Both are STEM professionals. One spends everything on lifestyle. 401k match and that’s it. The other one invests $2,000/mo into a Roth IRA and brokerage. DCA. Index funds. Dividends. In 30 years: One is still working. The other one retired with $2,048,692. Tax-free. Same salary. Different system.