Your worst enemy is inertia.

你最大的敌人就是惰性。

youdao

How would your worst enemy describe you?

你最大的敌人是如何描述你的？

youdao

Be your own best friend not your worst enemy.

做自己最好的朋友，而非最坏的敌人。

youdao

Just as compound interest is your best friend when you're saving money, it's your worst enemy when you owe money.

FORBES: Magazine Article

Your ego can be your worst enemy particularly for male investors.

FORBES: When Betting On Stocks, Wait Before Lighting That Victory Cigar

The fact is, in the case of trying to pick the right stocks or time the market your actions are your own worst enemy.

FORBES: Market Volatility: A Call to Inaction!