Leverage is the only way where smart people got dumb by Warren Buffett:

Warren Buffett has famously said that leverage is the main means by which intelligent people can make enormous financial blunders. He feels that if you’re a good investor, you don’t require leverage, and if you have no ability to invest, leverage will most certainly ruin you. In essence, leverage, or borrowing to invest, can magnify both profits and losses, and Buffett contends that the dangers of amplified losses outweigh the gains for people who are already experienced and successful at investing. Here is a more detailed description:
The Risk of Amplified Losses:
Leverage amplifies the effect of market moves. While it can be used to enhance returns when investments are good, it also signifies that losses are increased when investments go down.
For the Unskilled, Leverage is Destructive:
Buffett’s approach is that if you know how to invest, you can get good returns without borrowing. His interest is on preserving capital and long-term value investing.
Buffett is convinced that individuals who do not possess the knowledge and expertise needed in investing are especially exposed to leverage risk. They might not be able to cope with the higher risk and could end up with huge losses.
Buffett’s Own Experience:
Buffett and his business partner Charlie Munger share a deep dislike of leverage, eschewing it wherever possible in their investment approach. They’ve witnessed the devastating effects of leverage for themselves, even on those possessing remarkable financial brains.
“If you’re smart, you don’t need it; if you’re dumb, it’ll ruin you
This reference, ascribed to Buffett, summarizes his perspective of leverage. It reminds us that leverage is only useful to individuals who already have the ability and self-discipline to handle its risks.