setback · reverse · check · defeat · frustration · disappointment · to frustrate · to discourage · to set sb back · to blunt · to subdue

There will be setbacks and false starts. There are many who won't agree with every decision or policy I make as president. And we know the government can't solve every problem.

He overcame all sorts of hardship and setbacks to succeed in a solo crossing of Antarctica.

How frustrated must a person be to commit suicide?

There's an upside to everything so it's unnecessary to focus on the good; on the contrary, we should instead be pushing for reversals because it's only through setbacks that we improve and see decisive opportunities clearly.