First my apologies to PETA, the organization that has determined this well-known phrase should be changed to the more animal-friendly "put all your berries in one bowl."
Many people disagree when it comes to investment advice, but everyone seems to agree with the concept of diversification. That is, you should not have all your money in one equity, one fund, or in one sector. You need to diversify across multiple asset classes so that no one thing can wipe you out. In fact, I have never heard anyone disagree with this concept.
And yet when it comes to income, the vast majority of people have no diversification. Most people work for one company and rely on a single paycheck. Perhaps this approach was more sustainable years ago when companies and employees were both loyal to each other. In today's world this approach can lead to disaster.
Whether you are a high performer or have in-demand skills, there is no guarantee that your job is safe. Companies merge or buy out other companies and poof your job can be eliminated. As you get older the risk is worse because someone younger who may be less experienced but is willing to take less pay could replace you. Yes that is age discrimination but it happens.
The answer is to figure out a way to create multiple streams of income. This could be another job. It could be saving money and using that money to make more money. It could be starting a company or producing content on one or many platforms. In our history and culture there has never been a better time to maximize your talents by leveraging technology and getting direct access to customers.
It is hard to change mindset and make this happen. I think it gets harder as you get older. I'm still trying anyway because it's worth it.