I like to revisit history and look for parallels. This is a long blog post from Jason Zweig but it is very much worth your time. 

History don't repeat but it does rhyme.

https://jasonzweig.com/from-the-archives-baloney-com/

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In Summary

"In May 1999, I advised readers to steer clear of Internet stocks, a stance that was far from obvious at the time. The prevailing belief was that these companies would experience unprecedented growth without slowing down. For instance, Monument Internet Fund's manager, Alexander Cheung, projected a 50% annual return over the next three to five years and an average of 35% annually over the next two decades.

While the Internet has indeed transformed the world, surpassing even the most optimistic expectations from 1999, investors paid exorbitant prices to participate in this revolution. Historical patterns demonstrate that growth rates are finite and tend to decline over time. No company or industry can sustain rapid growth indefinitely without eventually exhausting new customers and profit sources. Moreover, early leaders in emerging industries often don't become the long-term winners.

As Benjamin Graham observed in 1934 regarding the 1929 bull market, the "new-era" thinking led investors to disregard traditional valuation standards, resulting in the purchase of stocks at inflated prices. In 1999, this mindset extended to companies with no earnings, based on the assumption of virtually infinite future profits.

Pointing out these irrationalities was unpopular at the time, and I received numerous emails criticizing my perspective. However, by mid-2000, as the dot-com bubble burst, those messages ceased. The key takeaway is that when a transformative investment idea emerges, early skeptics are often dismissed. As the idea gains popularity and becomes accepted wisdom, it can lead to market bubbles. When questioning the prevailing belief becomes viewed as irrational, it's a signal that the bubble may be nearing its end.

In summary, while the Internet's potential was real, the investment frenzy of the late 1990s led to unsustainable valuations. Recognizing the limits of growth and adhering to sound valuation principles are essential to avoid the pitfalls of market bubbles."