Roses will always have thorns but with care they can be avoided.

玫瑰花上都有刺，不过只要小心就碰不到。

...the shade of a thorn bush.

一丛荆棘下的阴凉

...the thorn and bramble thickets.

荆棘密布的灌木丛

She's a real thorn in his side.

她真叫他头疼。

The Party was a thorn in the flesh of his coalition.

该党是他所在联盟的眼中钉、肉中刺。