I'm a natural pessimist; I usually expect the worst.

我是个天生的悲观主义者，我总是往最坏的方面想。

《柯林斯英汉双解大词典》

Always expect the worst.

永远准备最坏的情况。

youdao

If you expect the worst, the worst will happen.

如果你总是期待坏的事情发生，那坏事情一定会发生。

youdao

They expect the worst from a regime they fear can now act without restraint.

BBC: Syria crisis: Fear and abandonment in under-fire Homs

They said they expect the worst financial crisis in more than a half century is going to get even worse.

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"With stocks, I always expect the worst but hope for the best, " said the 48-year-old, who previously founded investment bank ThinkEquity.

WSJ: Facebook Fever: GSV Capital Investment Doubles in Just 6.5 Hours