You've probably read blog posts and articles that recommend a certain brand of backpack or water, so you click on their hyperlinked link. Oftentimes, that person gets paid a commission when you do. If you have a blog, the same can happen for you. It's a win-win-win for everyone involved — you, the product you're recommending, and the person who clicks on the link to get the product. Pat Flynn talks about this at length on his website, Smart Passive Income, where you can learn a whole lot more on the topic, aside from affiliate marketing.
You must sacrifice the pleasures of today for the freedom you will earn tomorrow. In my 20s, I shared a studio with my best friend from high school and drove beater cars worth less than 10% of my annual gross income. I'd stay until after 7:30 p.m. at work in order to eat the free cafeteria food. International vacations were replaced with staycations since work already sent me overseas two to four times a year. Clothes were bought at thrift shops, of course.
An obvious example is over exposure to bank stocks, which have been excellent investments for over a century.  Though a foundation of most portfolios, bank stocks do involve more risk at certain stages of the economic cycle than many realise.  Being less exposed to bank shares in the last few months could have preserved some capital.  So, a more diversified approach can help mitigate some of these risks.