Let's say you're 25 years old. Let's say you can save 10 000$ a year. It's ambitious, but many people could do it if they put a little effort in it. Let's say you have enough investment knowledges to manage your money in a way that you can get the performance of the market which is about 10% a year. Otherwise, just buy a fund that reproduces the performance of the market and you'll be OK.
Here's what it would look like over time:
25 years old: 10 000$ (savings)
26 years old: 11 000$ (savings + performance) + 10 000$
27 years old: 24 200$ + 10 000$
28 years old: 37 620$ + 10 000$
29 years old: 52 382$ + 10 000$
30 years old: 68 620$ + 10 000$
31 years old: 86 482$ + 10 000$
32 years old: 106 130$ + 10 000$
33 years old: 127 743$ + 10 000$
34 years old: 151 518$ + 10 000$
35 years old: 177 670$ + 10 000$
36 years old: 206 436$
Here you are: 36 years old and you have a portfolio of 206 436$ after only 12 years of savings. And now, each year, your portfolio should grow by about 20 000$ without any effort. In other words, your income is now 20 000$ higher than all the people around you who didn't put any money on the stock market. If you continue like that just a few years, you'll get 30 000$ a year before you're 40.
Some people call it the power of compounding. I call it the power of discipline. In fact, it's a combination of both. Isn't it fabulous? Your income is now a kind of bonus because there's a mountain that keeps growing besides you without any effort.
Keep your discipline;
If your portfolio goes down, continue to invest;
If your portfolio goes up, continue to invest;
Continue up to a point where you don't see the point of investing some of your income because it's too marginal versus the size of your portfolio. That's when you'll know that you are rich.